fantasy vs imaginativeness

fantasy and imaginativeness both are nouns.

Word	Noun	Adjective	Verb	Adverb
fantasy	Yes	No	Yes	No
imaginativeness	Yes	No	No	No

As nouns, imaginativeness is a hypernym of fantasy; that is, imaginativeness is a word with a broader meaning than fantasy:

fantasy: imagination unrestricted by reality
imaginativeness: the formation of a mental image of something that is not perceived as real and is not present to the senses

Other hypernyms of fantasy include imagination, vision.

fantasy (noun)	imaginativeness (noun)
imagination unrestricted by reality	the formation of a mental image of something that is not perceived as real and is not present to the senses
something many people believe that is false
fiction with a large amount of imagination in it

fantasy (verb)	imaginativeness (verb)
indulge in fantasies