Last week during Sunday School our instructor read us a letter to the admissions committee at BYU. After the first sentence, which read " . . . and I am an alumni of BYU." I turned to my neighbors and we shook our heads. This is a common error around here, but there is no such thing as an alumni. Of any institution.
This is because alumni is a Latin word and the endings change based on the gender and number of people you're talking about. If you are talking about one man, he is an alumnus. If you are talking about a single woman, she is an alumna. If there is a group of women only, they are alumnae and if you are speaking of a group of either all men or men and women, they are alumni. If you don't believe everything you read on the internet, you can check here or here or here.
This is why people get confused. For example, the Alumni Association, the Alumni House and Alumni Board are all correct uses, because they're talking about the whole group, male and female who have attended the institution. But that means that people are often unaware of the other forms. Like the woman who worked in Alumni Relations and kept correcting my husband when he told her I was an alumna.
Now if this is too much to remember, you can just say you "graduated from X" or "matriculated at X" and you'll do just fine. And if you already knew all this, you can go read Zina's malaprop post, which is really high art (or homonym hell). These posts make me want to laugh, cry and vomit simlutaneously.