colloquialism vs plainly

colloquialism is a noun but plainly is not a noun.

Word	Noun	Adjective	Verb	Adverb
colloquialism	Yes	No	No	No
plainly	No	No	No	Yes

colloquialism (noun)	plainly (noun)
a colloquial expression; characteristic of spoken or written communication that seeks to imitate informal speech

colloquialism (adverb)	plainly (adverb)
	unmistakably (`plain' is often used informally for `plainly')
	in a simple manner; without extravagance or embellishment