mental process vs cognition

mental process and cognition both are nouns.

Word	Noun	Adjective	Verb	Adverb
mental process	Yes	No	No	No
cognition	Yes	No	No	No

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

mental process: (psychology) the performance of some composite cognitive activity; an operation that affects mental contents
cognition: the psychological result of perception and learning and reasoning

Other hypernyms of mental process include knowledge, noesis.

mental process (noun)	cognition (noun)
(psychology) the performance of some composite cognitive activity; an operation that affects mental contents	the psychological result of perception and learning and reasoning