mental lexicon vs language

mental lexicon and language both are nouns.

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

mental lexicon (noun)	language (noun)
a language user's knowledge of words	the mental faculty or power of vocal communication
	the cognitive processes involved in producing and understanding linguistic communication
	a systematic means of communicating by the use of sounds or conventional symbols
	(language) communication by word of mouth
	the text of a popular song or musical-comedy number
	a system of words used to name things in a particular discipline