The abbreviation cf. (short for the Latin: confer, meaning "compare") is used in writing to refer the reader to other material to make a comparison with the topic being discussed. It is used to form a contrast, for example: "Abbott (2010) found supportive results in her memory experiment, unlike those of previous work (cf. Zeller & Williams, 2007)." It is recommended that "cf." be used only to suggest a comparison, and the word "see" be used to point to a source of information.
In biological naming conventions, cf. is commonly placed between the genus name and the species name to describe a specimen that is difficult to identify because of practical difficulties, such as the specimen being poorly preserved. For example, "Barbus cf. holotaenia" implies that the specimen is believed to be Barbus holotaenia but the actual identification cannot be certain.
Cf. can also be used to express a possible identity, or at least a significant resemblance, such as between a newly observed specimen and a known species or taxon. Such a usage might suggest a specimen's membership of the same genus or possibly of a shared higher taxon, such as in, "Diptera: Tabanidae, cf. Tabanus", where the author is confident of the order and family (Diptera: Tabanidae), but can only offer the genus (Tabanus) as a suggestion and has no information favouring a particular species.
There is a distinction between see and cf.; use cf. only to mean 'compare' or 'see, by way of comparison'.