make-believe vs imagination

make-believe and imagination both are nouns.

Word	Noun	Adjective	Verb	Adverb
make-believe	Yes	Yes	No	No
imagination	Yes	No	No	No

As nouns, imagination is a hypernym of make-believe; that is, imagination is a word with a broader meaning than make-believe:

Other hypernyms of make-believe include imagery, imaging, mental imagery.

make-believe (noun)	imagination (noun)
the enactment of a pretense	the formation of a mental image of something that is not perceived as real and is not present to the senses
imaginative intellectual play	the ability to form mental images of things or events
	the ability to deal resourcefully with unusual problems

make-believe (adjective)	imagination (adjective)
imagined as in a play