explanation vs mentation

explanation and mentation both are nouns.

Word	Noun	Adjective	Verb	Adverb
explanation	Yes	No	No	No
mentation	Yes	No	No	No

As nouns, mentation is a hypernym of explanation; that is, mentation is a word with a broader meaning than explanation:

Other hypernyms of explanation include cerebration, intellection, thinking, thought, thought process.

explanation (noun)	mentation (noun)
thought that makes something comprehensible	the process of using your mind to consider something carefully
a statement that makes something comprehensible by describing the relevant structure or operation or circumstances etc.
the act of explaining; making something plain or intelligible