In Italian, as in Latin, the letter i at the end of a word denotes a plural. That means that, no, you are not “an alumni” of West Central North Jefferson Technical College, you are an alumnus (or an alumna, if you are a female) of that fine institution. Alumni is the plural of alumnus (alumnae is the plural of alumna).
This also means that you did not have “raviolis” for lunch. Ravioli is already plural. So is spaghetti. And macchieroni (a.k.a. macaroni). And for the love of Sonja Henie’s tutu, panini! The next person who says “we had paninis for lunch” is getting clocked.
Think about the Magi who visited Jesus. (One of them would have been a Magus. Yes, like an Animagus. Exactly like an Animagus.) Think about the Illuminati. Think about something, anything, in your sphere of understanding that has an i on the end for the plural, and generalize, people!
In a somewhat related vein: those long, funny looking flowers on the altar in every Baptist church you’ve ever been in are not “gladiolas.” There is no such word as “gladiolas,” much less “gladiola.” One such flower is a gladiolus, which means that a multiplicity of them are gladioli. Like, well, Animagi.
Yes, like Animagi. Exactly like Animagi.