speech vs mental lexicon

speech and mental lexicon both are nouns.

Word	Noun	Adjective	Verb	Adverb
speech	Yes	No	No	No
mental lexicon	Yes	No	No	No

speech (noun)	mental lexicon (noun)
the mental faculty or power of vocal communication	a language user's knowledge of words
(language) communication by word of mouth
the act of delivering a formal spoken communication to an audience
words making up the dialogue of a play
a lengthy rebuke
the exchange of spoken words
your characteristic style or manner of expressing yourself orally
something spoken