The Unit

The Unit is an American action-drama television series that aired on CBS from March 7, 2006, to May 10, 2009. The series focuses on a top-secret military unit modeled after the real-life U.S. Army special operations unit commonly known as Delta Force.

On May 19, 2009, CBS announced the cancellation of the series after four seasons and 69 episodes.[1]

The Unit
The Unit 2006 Intertitle
Created byDavid Mamet
Based onInside Delta Force: The Story of America's Elite Counterterrorist Unit
By Eric L. Haney
StarringDennis Haysbert
Regina Taylor
Scott Foley
Robert Patrick
Audrey Marie Anderson
Max Martini
Abby Brammell
Demore Barnes
Michael Irby
Nicole Steinwedell
Theme music composerRobert Duncan
Opening theme"Fired Up" (Seasons 1–2)
"Walk the Fire" (Season 3–4)
Country of originUnited States
Original language(s)English
No. of seasons4
No. of episodes69 (list of episodes)
Executive producer(s)David Mamet
Shawn Ryan
Vahan Moosekian
Todd Ellis Kessler
Daniel Voll
Carol Flint
Producer(s)Sharon Lee Watson
Eric L. Haney
Norman S. Powell
CinematographyKrishna Rao
Michael Stecher
Checco Varese
Giovanni Lampassi
Editor(s)Rick Tuber
Devon Greene
David Koeppel
David Kaldor
Farrel Levy
Erik Presant
Ian Harbilas
Running time42 minutes
Production company(s)David Mamet Chicago
Bay Kinescope Boston
MiddKid Productions
20th Century Fox Television
Distributor20th Television
Original networkCBS
Picture format480i (SDTV)
1080i (HDTV)
Original releaseMarch 7, 2006 –
May 10, 2009


Based on show producer Eric L. Haney's book, Inside Delta Force: The Story of America's Elite Counterterrorist Unit (ISBN 0-440-23733-5), The Unit was created for television and executive produced by David Mamet and Shawn Ryan. The show is produced by The Barn Productions Inc., David Mamet Entertainment, and Fire Ants Films in association with 20th Century Fox Television.

The show purports to describe the daily lives of Delta Force (called "The Unit" in the show) operators during training and operational missions, as well as their families back home.

Internationally, The Unit premiered on October 3, 2006, in the United Kingdom on Bravo; on October 11, 2006, in Australia on the Seven Network, and on FOX8 and Arena on Foxtel/Austar pay-TV network and now airs on 7Two on Tuesdays at 8:30 pm; on January 11 in Spain on La Sexta; on January 25 in the Netherlands on RTL 5; on March 7 in Germany on Sat. 1; on September 23 in Bulgaria on bTV; on March 9, 2008, in Russia on DTV; and on June 13, 2009, in Vietnam on VTC7-Today TV, in Sri Lanka by Hiru TV in 2012, in Turkey by TNT, and in Indonesia on Global TV.

The theme music for the first and second seasons was "Fired Up" by Robert Duncan. Although the show focuses on an Army special ops unit, "Fired Up" is an adaptation of a Marine Corps running cadence called "Fired Up, Feels Good". Duncan also created "Walk the Fire", a 22-second segment used as a theme since season three.


"The Unit" is the U.S. Army colloquial term for Delta Force. Its recruits are selected from the Army (primarily from the 75th Ranger Regiment and Special Forces groups). The few who pass selection then undergo several more years of sophisticated and rigorous training for counterterrorism, reconnaissance, and direct-action missions. In a television interview, series creator Eric Haney—who is a former Delta Force operator—stated that the term "Delta Force" is never used in the spec ops community. They are only referred to as "The Unit" and their DOD designation is "Combat Applications Group". The official cover name of the unit in the show is the "303rd Logistical Studies Group". In the third season's premiere, an onscreen read-out identifies the Unit as "1st Special Actions Group".

The Unit is based at a fictional army post, "Fort Griffith". The location of Fort Griffith is never explicitly stated, but in episode 103, a bank statement of the lead character clearly shows an address for Fort Griffith, MO 63021, which puts it a few miles west of St. Louis. Other episodes make clear references to Greenwood, including mentions of Greenwood/Fort Griffith area, and local Greenwood police cars, as well as Missouri license plates clearly appear in many episodes. Greenwood, Missouri, is a small town located southeast of Kansas City. However, the red, white, and blue license plate is from the state of Idaho. This license plate can be seen in almost all the episodes. Unit members also wear the shoulder sleeve insignia of the inactivated 24th Infantry Division on their class A uniforms, as well as the shoulder crest of the 504th Parachute Infantry Regiment, "Strike Hold", currently part of the 1st BCT of the 82nd Airborne Division. In later episodes, unit members are shown as wearing the Special Operations Command patch on their class A uniforms.

The unit's immediate chain of command goes to the commanding officer, Colonel Tom Ryan—and, presumably, straight to the President of the United States. It's unknown whether or not this bypasses the command hierarchy, though in the season-four episode, "The Spear of Destiny", a side character receives confidential mission information and when questioned on who sent her, replies, "the Secretary of Defense". However, in the episode, "The Broom Cupboard", the President gives orders directly to Jonas for a unit mission.

The wives of the unit's Alpha Team personnel are given minimal mission or operational information. They are responsible for maintaining the "303rd Logistical Studies Group" cover in all interactions with anyone who is not a unit family member. Their husbands are, in fact, still performing highly dangerous missions, but they are not permitted to know specifics, such as where their husbands are deployed, of what their training routines consist, how long their assignments will last, or even if their husbands are safe.

If a member of the unit is killed in action, the actual mode of death is not told to the families. A cover story concurrent with a member of the 303 Logistical Studies Unit is created. The wives themselves are encouraged to form a close, cohesive military family based on the common knowledge and strife to which this inevitably leads.

The unit has an unconventional structure. With the size of a company—about 130 operators—it is commanded by a colonel (companies are usually commanded by captains; colonels usually command elements such as brigades or regiments). This is parallel to Delta's structure, which was implemented by Col. Charles Alvin Beckwith. The CO, Colonel Ryan, normally wears a "sanitized" uniform (bearing absolutely no tapes, such as his name, or even U.S. Army, or rank insignia).

Whereas a Special Forces Operational Detachment–Alpha (ODA) is commanded by a captain, the unit sends five-man teams into the field under noncommissioned officers, such as the team led by Command Sergeant Major Jonas Blane, the Unit's NCOIC of Alpha Team. Their soldiers possibly have the same Special Forces specialties as in Army Special Forces. An ODA, formerly known as an "A-Team", has weapons sergeants, engineering sergeants, medical sergeants, communications sergeants, etc.

The wives, if suspected of speaking about the unit's existence, can cause their husbands to be expelled and returned to regular Army service. Colonel Ryan has stated, time and again, that this can ruin a soldier's career, as well as his marriage, and has also stated that he will not hesitate to destroy families to preserve the unit's security. He has also threatened the wives with closing the unit down, and restarting it somewhere else under another cover—forcing the uprooting of all families involved.

The unit deploys throughout the world, and both the Army and United States government have the ability to deny the existence of the unit and any of its members to prevent the onset of international incidents. Their uniforms are commonly not standard Army issue, which makes denying their connection with the US Army easier if they are killed or captured. They also carry weapons that are not always standard issue, and the unit's personnel are familiar with weapons from around the world and can make themselves look like military personnel from other organizations. Unit members can and are sometimes also working as protection details for U.S. diplomats on visits overseas, as well as foreign dignitaries and State Department-designated VIPs on U.S. soil, in which cases they are attached to the Diplomatic Security Service and do carry the official DSS Special Agent badge.

The unit's members frequently use code names such as Snake Doctor, Dirt Diver, Betty Blue, Cool Breeze, and Hammer Head, as well as colors (Mr. White, Green, Blue, Black). These are usually used when working directly with American civilians, other English speakers not trained for emergencies, or on counterterrorism missions. According to Jonas Blane, the order of precedence for his team after he is disabled, is, from top to bottom: Mack Gerhardt, Charles Grey, Hector Williams, and Bob Brown based on seniority.


Season Episodes Originally aired
Season premiere Season finale
1 13 March 7, 2006 May 16, 2006
2 23 September 19, 2006 May 8, 2007
3 11 September 25, 2007 December 18, 2007
4 22 September 28, 2008 May 10, 2009


Actor Role Callsign Season
Dennis Haysbert Sergeant Major** Jonas Blane Snake Doctor 1–4
Regina Taylor Molly Blane 1–4
Scott Foley Sergeant First Class** Bob Brown Cool Breeze 1–4
Audrey Marie Anderson Kim Brown 1–4
Max Martini Master Sergeant** Mack Gerhardt Dirt Diver 1–4
Abby Brammell Tiffy Gerhardt 1–4
Michael Irby Sergeant First Class Charles Grey Betty Blue 1–4
Bre Blair Joss Grey* 4
Robert Patrick Brigadier General** Thomas Ryan Dog Patch 06/Blue Iguana 1–4
Rebecca Pidgeon Charlotte Ryan* 1–4
Demore Barnes Sergeant First Class Hector Williams Hammer Head 1–3
Nicole Steinwedell Warrant Officer One Bridget Sullivan Red Cap 4
Wes Chatham Staff Sergeant Sam McBride Whiplash 4
Kavita Patil Sergeant Kayla Medawar 1–4
Angel Wainwright Second Lieutenant Betsy Blane 1–4
Alyssa Shafer Serena Brown 1–4


^** Continuity errors frequently occur regarding the rank of Jonas Blane. In "Pandemonium, Part 2", Blane states his rank as command sergeant major, his uniform rank is sergeant major. In the United States Army, however, soldiers are often laterally transitioned between the ranks depending on their assignments. Command sergeants major are also addressed as "sergeant major" when in conversation, not "command sergeant major". This is similar to the practice (in the Army) whereby staff sergeants or sergeants first class are addressed simply as "sergeant".

^** Promoted from staff sergeant during "Side Angle Side".

^** Although this might have just been dirty talk, a similar continuity error exists regarding the rank of Mack Gerhardt. In the season-one episode "True Believers", his wife says to him "come here sergeant major, and give me a report", but his rank is later established as master sergeant. In the final wedding scene of season four, however, Mack is shown with E-7, or sergeant first class, rank on his uniform.

^** Promoted from colonel during "Unknown Soldier"

^* Formerly Morgan; married Grey in "Unknown Soldier"

^* Formerly Canning; married Ryan in "The Wall"


The program features both the domestic lives of the team members and their missions abroad, in addition to the effects their careers have on their home lives, wives, and girlfriends. It premiered in the United States on March 7, 2006, on CBS as a midseason replacement. The second season debuted on September 19, 2006.

The third season started on September 25, 2007, with a hiatus occurring after the 11th episode due to 2007–08 Writers Guild of America strike. The show was picked up for a fourth and final season by CBS on May 12, 2008.[2]

The fourth and final season began on September 28, 2008, and concluded on May 10, 2009. On May 19, 2009, it was announced that, after four seasons and 69 episodes, the series had been cancelled by CBS,[3] but on the same day, producers at 20th Century Fox Television announced that the reruns of the show would be broadcast in syndication, in stations covering 56% of the country already committed to carrying the show, including the Fox Television Stations.[4]

Main crew

Series directed by:

Series writing credits:

  • David Mamet (67 episodes, 2006–2009)
  • Eric L. Haney (66 episodes, 2006–2009)
  • Randy Huggins (25 episodes, 2006–2009)
  • Emily Halpern (24 episodes, 2006–2007)
  • Lynn Mamet (12 episodes, 2006–2009)
  • Sterling Anderson (12 episodes, 2006)
  • Sharon Lee Watson (10 episodes, 2006–2009)
  • Todd Ellis Kessler (8 episodes, 2006–2009)
  • Daniel Voll (5 episodes, 2006–2008)
  • Paul Redford (4 episodes, 2006)
  • Ted Humphrey (4 episodes, 2008–2009)
  • Dan Hindmarch (3 episodes, 2006–2009)
  • Frank Military (3 episodes, 2007–2008)
  • Shawn Ryan (2 episodes, 2006–2007)
  • Carol Flint (2 episodes, 2006)
  • Peter Blaber (2 episodes, 2008–2009)
  • Patrick Moss (2 episodes, 2008–2009)
  • Benjamin Daniel Lobato (2 episodes, 2009)


Seasonal ratings

Season Episodes Originally aired Viewers
Season premiere Season finale Time slot (ET)
1 2005–06 13 March 7, 2006 May 16, 2006 Tuesday at 9:00 pm 15.5[5] 14[5]
2 2006–07 23 September 19, 2006 May 8, 2007 11.1[6] 36[6]
3 2007–08 11 September 25, 2007 December 18, 2007 10.7[7] 37[7]
4 2008–09 22 September 28, 2008 May 10, 2009 Sunday at 10:00 pm 10.0 43

DVR Ratings:

  • season 4 (9/22/08 - 11/23/08): 1.37 million [1]

Awards and nominations

Year Award Category Work Outcome
2006 Primetime Emmy Awards Outstanding Stunt Coordination Norman Howell (stunt coordinator)
For episode "First Responders".
Casting Society of America, USA Artios Best Dramatic Pilot Casting Sharon Bialy, and Sherry Thomas
For episode "First Responders (#1.1)".
2007 Screen Actors Guild Awards Outstanding Performance by a Stunt Ensemble in a Television Series Kanin Howell (stunts) Nominated
ASCAP Film and Television Music Awards 2007 Top TV Series Robert Duncan Won
Hollywood Post Alliance, US 2007 Outstanding Compositing - Television Bob Minshall, Matt von Brock, Changsoo Eun, Dan Lopez, and Encore
For Episode: "Johnny B. Good"
Young Artist Awards 2007 Best Performance in a TV Series (Comedy or Drama) - Guest Starring Young Actor Alec Holden Nominated
Image Awards 2007 Outstanding Drama Series Nominated
Outstanding Actor in a Drama Series Dennis Haysbert Nominated
Outstanding Actress in a Drama Series Regina Taylor Nominated
2008 Image Awards 2008 Outstanding Actress in a Drama Series Regina Taylor Won
Outstanding Drama Series Nominated
Outstanding Actor in a Drama Series Dennis Haysbert Nominated
Screen Actors Guild Awards 2008 Outstanding Performance by a Stunt Ensemble in a Television Series
Troy Brown, Max Daniels, Steve M. Davison, Jeffrey J. Dashnaw, and Daniel Hernandez Nominated
Young Artist Awards 2008 Best Performance in a TV Series - Recurring Young Actress Danielle Hanratty Nominated
2009 Screen Actors Guild Awards 2009 Outstanding Performance by a Stunt Ensemble in a Television Series Troy Brown, J.J. Dashnaw, Eddie J. Fernandez, and Oakley Lehman Nominated
Image Awards 2009 Outstanding Drama Series Nominated
Outstanding Actor in a Drama Series Dennis Haysbert Nominated
Young Artist Awards 2009 Best Performance in a TV Series - Recurring Young Actress Danielle Hanratty Nominated
2010 Screen Actors Guild Awards 2010 Outstanding Performance by a Stunt Ensemble in a Television Series Troy Brown, Max Daniels, J.J. Dashnaw, and Oakley Lehman Nominated

Home media

DVD Name Region 1 Region 2 Region 3 Region 4
The Complete First Season September 19, 2006 April 30, 2007

France: July 4, 2007
Belgium: August 8, 2007

April 18, 2007 April 18, 2007
The Complete Second Season September 25, 2007 October 22, 2007 TBA March 4, 2008
The Complete Third Season October 14, 2008 October 20, 2008 TBA April 8, 2009
The Complete Fourth Season September 29, 2009 February 22, 2010 TBA May, 2010
The Unit: The Complete Giftset September 29, 2009 February 22, 2010 TBA May, 2010

Prospective fifth season storyline

According to an interview executive producer Shawn Ryan gave to The Futon Critic, "[David] Mamet and I and our writers, we came up with a lot of great stuff," Ryan said about his pitch to CBS executives for a potential fifth season. "It was going to be a whole new show in the sense that we were going to be training some young people, Bob was going to be training some people for a whole new organization. Jonas was finally going to be seeing his run end......The final season was going to be, I figured the fifth season was going to be the last... It was going to be a long, sort of final mission for Jonas. He's not medically cleared, Mack has to go in and sort of change the medical records so that Jonas can keep on [going on missions]. We had a whole thing planned, it was going to be good." Jonas would eventually leave the army due to his injuries coupled with combat stress and reunite with Molly. Mack would take over the team but at the end of the series would also leave for a training post after Tiffy becomes pregnant with their third child. Bob would be badly injured in a parachuting accident and join the CIA as their Unit liaison. Ryan would take a demotion to regain control of The Unit whilst Bridget Sullivan would be killed on a mission halfway through the season. Charles Grey would take over as team leader with Sam McBride as his deputy training replacements for the personnel they have lost.

Other storylines would include the recruitment of more female members, the team being hounded by human rights campaigners intent on bringing them to trial for their actions, the CIA creating its own rival commando force as a mirror image of The Unit, the search for a mole within the organization leaking information to the highest bidder, the Army's treatment of soldiers suffering debilitating injuries and combat stress and Sam McBride confiding to Bridget Sullivan that he is the Unit's first gay member.[8]


  1. ^ French, Dan (May 20, 2009). "'The Unit', 'Without A Trace' cancelled". Digital Spy. Retrieved October 29, 2018.
  2. ^ "Show Tracker". The Los Angeles Times. May 12, 2008.
  3. ^ ""The Unit," "Earl," "Medium" get the ax". Reuters. May 20, 2009.
  4. ^ Andreeva, Nellie (May 19, 2009). "'The Unit' to live in syndication". The Hollywood Reporter. Retrieved September 2, 2016.
  5. ^ a b "2005–06 primetime wrap". The Hollywood Reporter. May 26, 2006. Archived from the original on January 14, 2007. Retrieved February 15, 2010.
  6. ^ a b "2006–07 primetime wrap". The Hollywood Reporter. March 25, 2007. Archived from the original on January 29, 2010. Retrieved February 14, 2010.
  7. ^ a b "Season Program Rankings from 09/24/07 though 05/25/08". ABC Medianet. May 28, 2008. Retrieved February 14, 2010.
  8. ^ "Breaking News - Exclusive: Ryan Shares What Might Have Been on "The Unit"". 2014-02-15. Retrieved 2014-03-15.

See also

External links

AAR wheel arrangement

The AAR wheel arrangement system is a method of classifying locomotive (or unit) wheel arrangements that was developed by the Association of American Railroads. It is essentially a simplification of the European UIC classification, and it is widely used in North America to describe diesel and electric locomotives. It is not used for steam locomotives which use the Whyte notation instead.

The AAR system counts axles instead of wheels. Letters refer to powered axles, and numbers to unpowered (or idler) axles. "A" refers to one powered axle, "B" to two powered axles in a row, "C" to three powered axles in a row, and "D" to four powered axles in a row. "1" refers to one idler axle, and "2" to two idler axles in a row. A dash ("–") separates trucks, or wheel assemblies. A plus sign ("+") refers to articulation.


The ampere (; symbol: A), often shortened to "amp", is the base unit of electric current in the International System of Units (SI). It is named after André-Marie Ampère (1775–1836), French mathematician and physicist, considered the father of electrodynamics.

The International System of Units defines the ampere in terms of other base units by measuring the electromagnetic force between electrical conductors carrying electric current. The earlier CGS measurement system had two different definitions of current, one essentially the same as the SI's and the other using electric charge as the base unit, with the unit of charge defined by measuring the force between two charged metal plates. The ampere was then defined as one coulomb of charge per second. In SI, the unit of charge, the coulomb, is defined as the charge carried by one ampere during one second.

New definitions, in terms of invariant constants of nature, specifically the elementary charge, will take effect on 20 May 2019.


The Celsius scale, also known as the centigrade scale, is a temperature scale used by the International System of Units (SI). As an SI derived unit, it is used by all countries except the United States, the Bahamas, Belize, the Cayman Islands and Liberia. It is named after the Swedish astronomer Anders Celsius (1701–1744), who developed a similar temperature scale. The degree Celsius (symbol: °C) can refer to a specific temperature on the Celsius scale or a unit to indicate a difference between two temperatures or an uncertainty. Before being renamed to honor Anders Celsius in 1948, the unit was called centigrade, from the Latin centum, which means 100, and gradus, which means steps.

From 1743, the Celsius scale is based on 0 °C for the freezing point of water and 100 °C for the boiling point of water at 1 atm pressure. Prior to 1743, the scale was also based on the boiling and melting points of water, but the values were reversed (i.e. the boiling point was at 0 degrees and the melting point was at 100 degrees). The 1743 scale reversal was proposed by Jean-Pierre Christin.

By international agreement, since 1954 the unit degree Celsius and the Celsius scale are defined by absolute zero and the triple point of Vienna Standard Mean Ocean Water (VSMOW), a specially purified water. This definition also precisely relates the Celsius scale to the Kelvin scale, which defines the SI base unit of thermodynamic temperature with symbol K. Absolute zero, the lowest temperature possible, is defined as being exactly 0 K and −273.15 °C. The temperature of the triple point of water is defined as exactly 273.16 K (0.01 °C). This means that a temperature difference of one degree Celsius and that of one kelvin are exactly the same.On 20 May 2019, the kelvin, and along with it the degree Celsius, will be redefined so that its value will be determined by definition of the Boltzmann constant.

Commanding officer

The commanding officer (CO) or sometimes, if the incumbent is a general officer, commanding general (CG), is the officer in command of a military unit. The commanding officer has ultimate authority over the unit, and is usually given wide latitude to run the unit as they see fit, within the bounds of military law. In this respect, commanding officers have significant responsibilities (for example, the use of force, finances, equipment, the Geneva Conventions), duties (to higher authority, mission effectiveness, duty of care to personnel), and powers (for example, discipline and punishment of personnel within certain limits of military law).

In some countries, commanding officers may be of any commissioned rank. Usually, there are more officers than command positions available, and time spent in command is generally a key aspect of promotion, so the role of commanding officer is highly valued. The commanding officer is often assisted by an executive officer (XO) or second-in-command (2i/c), who handles personnel and day-to-day matters, and a senior enlisted advisor. Larger units may also have staff officers responsible for various responsibilities.

Crystal structure

In crystallography, crystal structure is a description of the ordered arrangement of atoms, ions or molecules in a crystalline material. Ordered structures occur from the intrinsic nature of the constituent particles to form symmetric patterns that repeat along the principal directions of three-dimensional space in matter.

The smallest group of particles in the material that constitutes this repeating pattern is the unit cell of the structure. The unit cell completely reflects the symmetry and structure of the entire crystal, which is built up by repetitive translation of the unit cell along its principal axes. The translation vectors define the nodes of the Bravais lattice.

The lengths of the principal axes, or edges, of the unit cell and the angles between them are the lattice constants, also called lattice parameters or cell parameters. The symmetry properties of the crystal are described by the concept of space groups. All possible symmetric arrangements of particles in three-dimensional space may be described by the 230 space groups.

The crystal structure and symmetry play a critical role in determining many physical properties, such as cleavage, electronic band structure, and optical transparency.

Cubic crystal system

In crystallography, the cubic (or isometric) crystal system is a crystal system where the unit cell is in the shape of a cube. This is one of the most common and simplest shapes found in crystals and minerals.

There are three main varieties of these crystals:

Primitive cubic (abbreviated cP and alternatively called simple cubic)

Body-centered cubic (abbreviated cI or bcc),

Face-centered cubic (abbreviated cF or fcc, and alternatively called cubic close-packed or ccp)Each is subdivided into other variants listed below. Note that although the unit cell in these crystals is conventionally taken to be a cube, the primitive unit cell often is not.

Delta Force

The 1st Special Forces Operational Detachment-Delta (1st SFOD-D), commonly referred to as Delta Force, Combat Applications Group (CAG), "The Unit", Army Compartmented Element (ACE), or within JSOC as Task Force Green, is an elite special mission unit of the United States Army, under operational control of the Joint Special Operations Command. The unit is tasked with specialized missions primarily involving hostage rescue and counter-terrorism, as well as direct action and special reconnaissance against high-value targets. Delta Force and its maritime counterpart, the U.S. Navy's SEAL Team Six (also known as the Naval Special Warfare Development Group or DEVGRU) are the U.S. military's primary counterterrorism units. Delta Force and DEVGRU perform the most complex, classified, and dangerous missions in the U.S. military, as directed by the U.S. National Command Authority.

Most Delta Force operators are selected from the United States Army Special Operations Command's elite Special Forces Groups and the 75th Ranger Regiment, as well as from other special operations units.


The gigabyte () is a multiple of the unit byte for digital information. The prefix giga means 109 in the International System of Units (SI). Therefore, one gigabyte is 1000000000bytes. The unit symbol for the gigabyte is GB.

This definition is used in all contexts of science, engineering, business, and many areas of computing, including hard drive, solid state drive, and tape capacities, as well as data transmission speeds. However, the term is also used in some fields of computer science and information technology to denote 1073741824 (10243 or 230) bytes, particularly for sizes of RAM. The use of gigabyte may thus be ambiguous. Hard disk capacities as described and marketed by drive manufacturers using the standard metric definition of the gigabyte, but when a 500-GB drive's capacity is displayed by, for example, Microsoft Windows, it is reported as 465 GB, using a binary interpretation.

To address this ambiguity, the International System of Quantities standardizes the binary prefixes which denote a series of integer powers of 1024. With these prefixes, a memory module that is labeled as having the size 1GB has one gibibyte (1GiB) of storage capacity.


The kibibyte is a multiple of the unit byte for quantities of digital information. The binary prefix kibi means 210, or 1024; therefore, 1 kibibyte is 1024 bytes. The unit symbol for the kibibyte is KiB.The unit was established by the International Electrotechnical Commission (IEC) in 1998, has been accepted for use by all major standards organizations, and is part of the International System of Quantities. The kibibyte was designed to replace the kilobyte in those computer science contexts in which the term kilobyte is used to mean 1024 bytes. The interpretation of kilobyte to denote 1024 bytes, conflicting with the SI definition of the prefix kilo (1000), used to be common.


The light-year is a unit of length used to express astronomical distances and measures about 9.46 trillion kilometres (9.46 x 1012 km) or 5.88 trillion miles (5.88 x 1012 mi). As defined by the International Astronomical Union (IAU), a light-year is the distance that light travels in vacuum in one Julian year (365.25 days). Because it includes the word "year", the term light-year is sometimes misinterpreted as a unit of time.

The light-year is most often used when expressing distances to stars and other distances on a galactic scale, especially in nonspecialist and popular science publications. The unit most commonly used in professional astrometry is the parsec (symbol: pc, about 3.26 light-years; the distance at which one astronomical unit subtends an angle of one second of arc).

Long ton

Long ton, also known as the imperial ton or displacement ton, is the name for the unit called the "ton" in the avoirdupois system of weights or Imperial system of measurements. It was standardised in the thirteenth century and is used in the United Kingdom and several other British Commonwealth of Nations countries alongside the mass-based metric tonne defined in 1799.

It is not to be confused with the short ton a unit of weight equal to 2,000 pounds (907.18474 kg) used in the United States, and in Canada before metrication, also referred to simply as a "ton".


The mebibyte is a multiple of the unit byte for digital information. The binary prefix mebi means 220; therefore one mebibyte is equal to 1048576bytes = 1024 kibibytes. The unit symbol for the mebibyte is MiB.

The unit was established by the International Electrotechnical Commission (IEC) in 1998. It was designed to replace the megabyte when used in the binary sense to mean 220 bytes, which conflicts with the definition of the prefix mega in the International System of Units (SI) as a multiplier of 106.

The binary prefixes have been accepted by all major standards organizations and are part of the International System of Quantities. Many Linux distributions use the unit, but it is not widely acknowledged within the industry or media.


The megabyte is a multiple of the unit byte for digital information. Its recommended unit symbol is MB. The unit prefix mega is a multiplier of 1000000 (106) in the International System of Units (SI). Therefore, one megabyte is one million bytes of information. This definition has been incorporated into the International System of Quantities.

However, in the computer and information technology fields, several other definitions are used that arose for historical reasons of convenience. A common usage has been to designate one megabyte as 1048576bytes (220 B), a measurement that conveniently expresses the binary multiples inherent in digital computer memory architectures. However, most standards bodies have deprecated this usage in favor of a set of binary prefixes, in which this quantity is designated by the unit mebibyte (MiB). Less common is a convention that used the megabyte to mean 1000×1024 (1024000) bytes.

Pascal (unit)

The pascal (symbol: Pa) is the SI derived unit of pressure used to quantify internal pressure, stress, Young's modulus and ultimate tensile strength. It is defined as one newton per square metre. It is named after the French polymath Blaise Pascal.

Common multiple units of the pascal are the hectopascal (1 hPa = 100 Pa) which is equal to one millibar, and the kilopascal (1 kPa = 1000 Pa) which is equal to one centibar.

The unit of measurement called standard atmosphere (atm) is defined as 101325 Pa. Meteorological reports in the United States typically state atmospheric pressure in millibars. In Canada these reports are given in kilopascals.

Percentage point

A percentage point or percent point is the unit for the arithmetic difference of two percentages. For example, moving up from 40% to 44% is a 4 percentage point increase, but is a 10 percent increase in what is being measured. In the literature, the percentage point unit is usually either written out, or abbreviated as pp or p.p. to avoid ambiguity. After the first occurrence, some writers abbreviate by using just "point" or "points".

Consider the following hypothetical example: In 1980, 50 percent of the population smoked, and in 1990 only 40 percent smoked. One can thus say that from 1980 to 1990, the prevalence of smoking decreased by 10 percentage points although smoking did not decrease by 10 percent (it decreased by 20 percent) – percentages indicate ratios, not differences.

Percentage-point differences are one way to express a risk or probability. Consider a drug that cures a given disease in 70 percent of all cases, while without the drug, the disease heals spontaneously in only 50 percent of cases. The drug reduces absolute risk by 20 percentage points. Alternatives may be more meaningful to consumers of statistics, such as the reciprocal, also known as the number needed to treat (NNT). In this case, the reciprocal transform of the percentage-point difference would be 1/(20pp) = 1/0.20 = 5. Thus if 5 patients are treated with the drug, one could expect to heal one more case of the disease than would have occurred in the absence of the drug.

For measurements involving percentages as a unit, such as, growth, yield, or ejection fraction, statistical deviations and related descriptive statistics, including the standard deviation and root-mean-square error, the result should be expressed in units of percentage points instead of percentage. Mistakenly using percentage as the unit for the standard deviation is confusing, since percentage is also used as a unit for the relative standard deviation, i.e. standard deviation divided by average value (coefficient of variation).


The petabyte is a multiple of the unit byte for digital information. The prefix peta indicates the fifth power of 1000 and means 1015 in the International System of Units (SI), and therefore 1 petabyte is one quadrillion (short scale) bytes, or 1 thousand billion (long scale) bytes. The unit symbol for the petabyte is PB.

1 PB = 1000000000000000B = 1015bytes = 1000terabytes.

A related unit, the pebibyte (PiB), using a binary prefix, is equal to 10245 bytes, which is more than 12% greater (250 bytes = 1125899906842624bytes).

One thousand petabytes (1000 PB) is equal to one exabyte (1 EB).


The terabyte is a multiple of the unit byte for digital information. The prefix tera represents the fourth power of 1000, and means 1012 in the International System of Units (SI), and therefore one terabyte is one trillion (short scale) bytes. The unit symbol for the terabyte is TB.

Unit circle

In mathematics, a unit circle is a circle with unit radius. Frequently, especially in trigonometry, the unit circle is the circle of radius one centered at the origin (0, 0) in the Cartesian coordinate system in the Euclidean plane. The unit circle is often denoted S1; the generalization to higher dimensions is the unit sphere.

If (x, y) is a point on the unit circle's circumference, then |x| and |y| are the lengths of the legs of a right triangle whose hypotenuse has length 1. Thus, by the Pythagorean theorem, x and y satisfy the equation

Since x2 = (−x)2 for all x, and since the reflection of any point on the unit circle about the x- or y-axis is also on the unit circle, the above equation holds for all points (x, y) on the unit circle, not only those in the first quadrant.

The interior of the unit circle is called the open unit disk, while the interior of the unit circle combined with the unit circle itself is called the closed unit disk.

One may also use other notions of "distance" to define other "unit circles", such as the Riemannian circle; see the article on mathematical norms for additional examples.

Unit testing

In computer programming, unit testing is a software testing method by which individual units of source code, sets of one or more computer program modules together with associated control data, usage procedures, and operating procedures, are tested to determine whether they are fit for use.

The Unit

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