Annwn vs imaginary place

Annwn and imaginary place both are nouns.

Word	Noun	Adjective	Verb	Adverb
Annwn	Yes	No	No	No
imaginary place	Yes	No	No	No

As nouns, imaginary place is a hypernym of Annwn; that is, imaginary place is a word with a broader meaning than Annwn:

Annwn: (Welsh mythology) the other world; land of fairies
imaginary place: a place that exists only in imagination; a place said to exist in fictional or religious writings

Other hypernyms of Annwn include fictitious place, mythical place.

Annwn (noun)	imaginary place (noun)
(Welsh mythology) the other world; land of fairies	a place that exists only in imagination; a place said to exist in fictional or religious writings