commonplace vs threadbare

commonplace is a noun but threadbare is not a noun.

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

As adjectives, commonplace and threadbare are synonyms defined as:

commonplace and threadbare: repeated too often; overfamiliar through overuse

Other synonyms of commonplace include banal, hackneyed, old-hat, shopworn, stock, timeworn, tired, trite, well-worn.

commonplace (noun)	threadbare (noun)
a trite or obvious remark

commonplace (adjective)	threadbare (adjective)
not challenging; dull and lacking excitement	repeated too often; overfamiliar through overuse
repeated too often; overfamiliar through overuse	having the nap worn away so that the threads show through
completely ordinary and unremarkable