The seventh edition of the Publication Manual of the American Psychological Association deems that it’s “officially good practice in scholarly writings to use the singular ‘they.’” Old-fashioned sentence structures like “A person should enjoy his or her vacation” will be replaced by “A person should enjoy their vacation” to include not only those who identify as he or she, but also other pronouns like “they,” “zir,” “ze,” “ve,” and so on.
The APA advises “they” be used in two cases: “(a) when referring to a generic person whose gender is unknown or irrelevant to the context and (b) when referring to a specific, known person who uses ‘they’ as their pronoun.”
Even when used as a singular pronoun, the APA advises that “they” be given a plural verb—“they are” instead of “they is.” “Themselves” and “themself” are also both acceptable to use when writing in APA style.
This endorsement by APA will be influential, as it is the largest scientific and professional organization of psychologists in the U.S. with over 118,000 members, according to Out. The Publication Manual is used by writers, researchers, editors, students, and educators in a wide variety of disciplines.