"pupil or graduate of a school," 1640s, from Latin alumnus "a pupil," literally "foster son," vestigial present passive participle of alere "to suckle, nourish," from PIE root *al- (2) "to grow, nourish." With ending akin to Greek -omenos. Plural is alumni. The fem. form is alumna (1882), plural alumnae.
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Definitions of alumna from WordNet
a person who has received a degree from a school (high school or college or university);