I am an alumnus/alumna - is the correct usage

"Alumni" (a plural form) is often used as a singular form for both genders; for example, "I am an alumni of the university," as opposed to "I am an alumnus/alumna of the university." This usage is erroneous in formal or historic usage. The prevalence of this usage is likely due to an ignorance of Latin grammar and the fact that printed documents and university merchandise almost always use the plural form of the word.
source: http://en.wikipedia.org/wiki/Alumni

FRENCH:

anglais            français
Alumnus:  ancien élève n. m.
Alumni:     anciens élèves n. f. 

CONVENTUM: Réunion des anciens élèves d'un établissement d'enseignement.  (merci Gilberte)
quasi-synonyme(s)  
réunion des anciens n. f.  
réunion de l'amicale des anciens n. f.
amicale n. f.   
conventum n. m. [Canada]