“Et al.” is a Latin term that means “and others,” and is used for in-text citations of works with multiple authors. The guidelines for using “et al.” vary slightly among the three major formatting styles. MLA uses “et al.” for works with three or more authors, while Chicago calls for using it with four or more authors. APA format requires that you cite all of the authors at the first mention if there are three, four, or five, and use “et al.” afterward. If there are at least six authors, then you may use “et al.” from the first mention. In all cases, you should use the last name of the first author followed by “et al.” in your in-text citation.