In citation, "cf" is an abbreviation for the Latin word "confer" or "conferatur," which means "compare". It is used to signal that the cited source supports a different claim or proposition than the one just made, and that it is worthwhile to compare the two claims and assess the difference. It is important to note that a "cf" source simply offers a different yet non-contradictory claim, and actual support to the claim just made should not be assumed. If the source gives a contradictory claim, a negative signal should be used. In MLA style, "cf" may be used in parenthetical citations, but writers should take care not to use the abbreviation when they intend to use "see also". Proper use of "cf" varies in several key ways, and it is classified as a signal indicating support rather than one of comparison.