think up vs invent

think up and invent both are verbs.

Word	Noun	Adjective	Verb	Adverb
think up	No	No	Yes	No
invent	No	No	Yes	No

As verbs, invent is a hyponym of think up; that is, invent is a word with a more specific, narrower meaning than think up:

Other hyponyms of think up include idealise, idealize, cook up, fabricate, make up, manufacture.

think up (verb)	invent (verb)
devise or invent	come up with (an idea, plan, explanation, theory, or principle) after a mental effort
	concoct something artificial or untrue