I received an e-mail informing me of the death of an alumni of the firm where I articled.
I was saddened by that news – he was a very nice guy – but also (albeit in a less significant way) by the writer’s choice of words.
The Latin singular is alumnus, meaning a foster-son – but also any male child who is a ward, charge or pupil.
By extension, alumnus came to be applied in the USA to former pupils or students. When universities went co-ed, the Latin alumna (foster-daughter, ward etc.) was available.
The plural of alumnus is alumni; if you have more than one female former student, they are alumnæ.
Sometimes alumni is used to refer to all former students, regardless of sex (or gender); alumni/æ is also seen. (I’m not a fan of using a slash for that kind of thing, but it’s functional.)
Alum is a nice way to way to be gender-neutral, and I suppose lends itself to the plural alums.
But an alumni? Never.
At Oxford, the old way was simply to call everyone who had left the university (or gone down, in traditional parlance) an old member, regardless of age.
Perhaps because this seemed ageist, alumnus and alumna are now officially used (after the predictable outcry from traditionalists, who saw it as yet another example of encroaching Americanism).
Old member does have the advantage of being easier to pluralise if you don’t know Latin.