I know Google is my friend..

[pat]

... but it still has not helped me answer this question:

What is the plural of alma mater? Does the designation apply to graduate schools one attended? (So one could in fact have more than one of them?)

Comments

[tenacious-snail.livejournal.com]

alma matrae?

(soul would be singular, and I'm guessin at "matrae" based on "mater, matris" as the entry in my Cassell's.)

[joedecker.livejournal.com]

The OED is silent on the spelling of any plurals. The phrase
is listed as non-naturalized or partially-naturalized, which would argue for
pluraization following Latin, not English rules. The definition
given suggests that "alma mater" is appropriate for Universities
and schools, suggesting that there's nothing logically wrong
with pluralization.

[hobbitbabe.livejournal.com]

I think it's usually used as the institution from which one gets one's undergraduate degree. (Don't know how that works for transfer students.) I have a graduate degree from an American university with fanatically-loyal alumni and alumnae, so I've thought about whether to refer to that institution as [one of] my alma mater, and I usually don't.