An all male group of graduates are called alumni
1 male graduate is an alumnus
1 female graduate is an alumna
An all female group of graduates are called alumnae
A mixed (both male and female) group of graduates are called alumni
 
Please note, whether the group is all male OR mixed they are still referred
to collectively as ALUMNI.

A tag, t-shirt, coffee mug, etc with "UGA Alumni" does not mean that you are referring to yourself as "an Alumni". It simply means that you are including yourself in that particular group. You would not have a tag, t-shirt, coffee mug, etc with "Georgia Bulldog".