objection vs gripe

objection and gripe both are nouns.

Word	Noun	Adjective	Verb	Adverb
objection	Yes	No	No	No
gripe	Yes	No	Yes	No

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

objection (noun)	gripe (noun)
(law) a procedure whereby a party to a suit says that a particular line of questioning or a particular witness or a piece of evidence or other matter is improper and should not be continued and asks the court to rule on its impropriety or illegality	informal terms for objecting
the act of protesting; a public (often organized) manifestation of dissent
the speech act of objecting
the act of expressing earnest opposition or protest

objection (verb)	gripe (verb)
	complain