truism vs commonplace

truism and commonplace both are nouns.

Word	Noun	Adjective	Verb	Adverb
truism	Yes	No	No	No
commonplace	Yes	Yes	No	No

As nouns, commonplace is a hyponym of truism; that is, commonplace is a word with a more specific, narrower meaning than truism:

Other hyponyms of truism include banality, bromide, cliche, platitude.

truism (noun)	commonplace (noun)
an obvious truth	a trite or obvious remark

truism (adjective)	commonplace (adjective)
	not challenging; dull and lacking excitement
	repeated too often; overfamiliar through overuse
	completely ordinary and unremarkable