expostulation vs expostulate

expostulation is a noun but expostulate is not a noun.

Word	Noun	Adjective	Verb	Adverb
expostulation	Yes	No	No	No
expostulate	No	No	Yes	No

expostulation (noun)	expostulate (noun)
the act of expressing earnest opposition or protest
an exclamation of protest or remonstrance or reproof

expostulation (verb)	expostulate (verb)
	reason with (somebody) for the purpose of dissuasion