Having read the recent meta discussion concerning the tag vocabulary and remembering that we prefer to have our tags in Latin, I started to wonder how one might translate the word "vocabulary" in Latin. What would be a good translation and why? I want to translate it in the context of tagging on this site. That is, if someone wants to learn Latin vocabulary, how could they describe their desire in Latin using a word or phrase that means "vocabulary"?
The obvious choice is vocabularium and it would make sense as a derivative, but it's not in Lewis and Short. A similar word, glossarium, can be found, but it seems to have an unsuitable nuance: glossa means "an obsolete or foreign word that requires explanation". My current preference is vocabularium (cf. vocabulum in L&S), but I'm not at all convinced that this is the optimal choice.