cf. is an abbreviation for the Latin word confer, meaning "compare."

It is sometimes used (primarily in dictionaries) to offer insight into the preceding word's etymology - i.e., to suggest how one term obtained its particular naming convention (perhaps from another phrase).

For example, the phrase "Big Whack (cf. Big Bang)" suggests to the reader that the usage of the simplified moniker Big Whack, used in lieu of the more formal term giant impact theory, stems from an earlier, similar use of the colloquial phrase Big Bang to describe the more technically complete definition "the hypothesized point in time when the observed expansion of the universe began."

• CF is a common abbreviation. See CF for other uses.