air castle vs dream

air castle and dream both are nouns.

Word	Noun	Adjective	Verb	Adverb
air castle	Yes	No	No	No
dream	Yes	No	Yes	No

As nouns, dream is a hypernym of air castle; that is, dream is a word with a broader meaning than air castle:

Other hypernyms of air castle include dreaming.

air castle (noun)	dream (noun)
absentminded dreaming while awake	a series of mental images and emotions occurring during sleep
	imaginative thoughts indulged in while awake
	a fantastic but vain hope (from fantasies induced by the opium pipe)
	a state of mind characterized by abstraction and release from reality
	a cherished desire
	someone or something wonderful

air castle (verb)	dream (verb)
	have a daydream; indulge in a fantasy
	experience while sleeping