5 Comments This discussion is locked.
I don't know exactly why but like many other languages, it's all about etymology (roots/origin(s) of the word) and usage. And as you said yourself nouns ending with -a are usually feminine. Keyword: usually. In other words, not all nouns ending with -a are feminine and not all feminine nouns end with -a.
masculine: un/el clima, problema, día
feminine: una/la canción, universidad, nube