And one man is an alumnus, two or more are alumni.

I'm not sure what you're saying or asking, but:

singular male: alumnus
singular female: alumna
plural male or mixed group (male and female, even if only one male): alumni
plural female: alumnae

These words are Latin, not Greek. But no, plurals in Greek (and in Latin) are not formed by adding s.


ETA: Cross-posted with DeltaBetaBaby and ladybug12.

Wow! I wish we had a Panhellenic Alumnae group in our area of Alabama, or if we do, I wish I would have known about it. That would have made life much easier in the last few months. My daughter is attending a SEC school and we have found recs for 14 of the chapters, but the other few worry me.

Ask the women who have given you recs if they know women in the sororities that you haven't gotten recs for, or if they know of an alumnae Panhel in the area.