AP Style holds that writers should distinguish between the words alumnus, alumni, alumna, and alumnae.
AP Style uses “alumnus” when referring to a man who has attended a school. It uses alumni as the plural of “alumnus.”
AP Style uses “alumna” when referring to a woman who has attended a school. It uses alumnae as the plural of “alumna.”
AP Style uses “alumni” to refer to a group of men and women who have attended a college.
For further reading, check out our full post on Alumnus and Alumna.