According to the United States National Center for Education Statistics, "scientific literacy is the knowledge and understanding of scientific concepts and processes required for personal decision making, participation in civic and cultural affairs, and economic productivity". A scientifically literate person is defined as one who has the capacity to:
The OECD PISA Framework (2015) defines scientific literacy as "the ability to engage with science-related issues, and with the ideas of science, as a reflective citizen." A scientifically literate person, therefore, is willing to engage in reasoned discourse about science and technology which requires the competencies to:
Finally, scientific literacy may involve particular attitudes toward learning and using science. A scientifically-literate citizen feels concerned about environmental and social issues, responsible to act on these issues, and empowered to use science as a tool in addressing these issues. A scientifically-literate citizen is research-oriented as he/she feels the need to search for something.
Reforms in science education in the United States have often been driven by strategic challenges such as the launch of the Sputnik satellite in 1957 and the Japanese economic boom in the 1980s. By contrast, scientific literacy is now taken to mean that everyone should have a working knowledge of science and its role in society. Science literacy is seen as a right of every person and a requirement for responsible members of society, one that helps average people to make better decisions and enrich their lives. The shift occurred in the late 1980s and early 1990s, with the publication of Science for All Americans and Benchmarks for Science Literacy.
Initial definitions of science literacy included elaborations of the actual content that people should understand, and this content often followed somewhat traditional lines (biology, chemistry, physics). Earth science was somewhat narrowly defined as expanded geological processes. In the decade after those initial documents, ocean scientists and educators revised the notion of science literacy to include more contemporary, systems-oriented views of the natural world, leading to scientific literacy programs for the ocean, climate, earth science, and so on. This shift has ensured that educators' views of science literacy stay in sync with the directions and advances of real science in the real world.
The interdependence of humans and our natural environment is at the heart of scientific literacy in the Earth systems. As defined by nationwide consensus among scientists and educators, this literacy has two key parts. First, a literate person is defined, in language that echoes the above definition of scientific literacy. Second, a set of concepts are listed, organized into six to nine big ideas or essential principles. This defining process was undertaken first for ocean literacy, then for the Great Lakes, estuaries, the atmosphere, and climate. Earth science literacy is one of the types of literacy defined for Earth systems; the qualities of an Earth science literate person are representative of the qualities for all the Earth system literacy definitions.
According to the Earth Science Literacy Initiative, an Earth-science-literate person:
All types of literacy in Earth systems have a definition like the above. Ocean literacy is further defined as "understanding our impact on the ocean and the ocean's impact on us". Similarly, the climate literacy website includes a guiding principle for decision making; "humans can take action to reduce climate change and its impacts". Each type of Earth systems literacy then defines the concepts students should understand upon graduation from high school. Current educational efforts in Earth systems literacy tend to focus more on the scientific concepts than on the decision-making aspect of literacy, but environmental action remains as a stated goal.
The theme of science in a socially-relevant context appears in many discussions of scientific literacy. Ideas that turn up in the life sciences include an allusion to ecological literacy, the "well-being of earth". Robin Wright, a writer for Cell Biology Education, laments "will [undergraduates'] misunderstandings or lack of knowledge about science imperil our democratic way of life and national security?" A discussion of physics literacy includes energy conservation, ozone depletion and global warming. The mission statement of the Chemistry Literacy Project  includes environmental and social justice. Technological literacy is defined in a three-dimensional coordinate space; on the knowledge axis, it is noted that technology can be risky, and that it "reflects the values and culture of society". Energy Literacy boasts several websites, including one associated with climate literacy and two advocacy organizations.
Attitudes about science can have a significant effect on scientific literacy. In education theory, understanding of content lies in the cognitive domain, while attitudes lie in the affective domain. Thus, negative attitudes, such as fear of science, can act as an affective filter and an impediment to comprehension and future learning goals. Studies of college students' attitudes about learning physics suggest that these attitudes may be divided into categories of real world connections, personal connections, conceptual connections, student effort and problem-solving.
The decision-making aspect of science literacy suggests further attitudes about the state of the world, one's responsibility for its well-being and one's sense of empowerment to make a difference. These attitudes may be important measures of science literacy, as described in the case of ocean literacy.
Proponents of scientific literacy tend to focus on what is learned by the time a student graduates from high school. Science literacy has always been an important element of the standards movement in education. All science literacy documents have been drafted with the explicit intent of influencing educational standards, as a means to drive curriculum, teaching, assessment, and ultimately, learning nationwide.
Programs to promote scientific literacy among students abound, including several programs sponsored by technology companies, as well as quiz bowls and science fairs. A partial list of such programs includes the Global Challenge Award, the National Ocean Sciences Bowl and Action Bioscience.
Some organizations have attempted to compare the scientific literacy of adults in different countries. The Organisation for Economic Co-operation and Development found that scientific literacy in the United States is not measurably different from the OECD average. Science News reports "The new U.S. rate, based on questionnaires administered in 2008, is seven percentage points behind Sweden, the only European nation to exceed the Americans. The U.S. figure is slightly higher than that for Denmark, Finland, Norway and the Netherlands. And it’s double the 2005 rate in the United Kingdom (and the collective rate for the European Union)." 
University educators are attempting to develop reliable instruments to measure scientific literacy, and the use of concept inventories is increasing in the fields of physics, astronomy, chemistry, biology and earth science.
Books on scientific literacy: