vocabulary vs cognition

vocabulary and cognition both are nouns.

Word	Noun	Adjective	Verb	Adverb
vocabulary	Yes	No	No	No
cognition	Yes	No	No	No

As nouns, cognition is a hypernym of vocabulary; that is, cognition is a word with a broader meaning than vocabulary:

vocabulary: a language user's knowledge of words
cognition: the psychological result of perception and learning and reasoning

Other hypernyms of vocabulary include knowledge, noesis.

vocabulary (noun)	cognition (noun)
a language user's knowledge of words	the psychological result of perception and learning and reasoning
the system of techniques or symbols serving as a means of expression (as in arts or crafts)
a listing of the words used in some enterprise