The term that refers to the vocabulary of a language, or the words contained within that language, is "lexicon." A lexicon is the complete set of words and word elements used in a particular language or subject area. It includes not only individual words but also bound morphemes and can cover specialized vocabularies in various fields. In linguistics, the lexicon functions as a catalogue of a language's words, distinct from grammar, which governs how words combine into sentences. Dictionaries typically list the lexicon of a language.
In summary, "lexicon" is the precise linguistic term for the vocabulary stock of a language.