water vapour vs vapor

water vapour and vapor both are nouns.

Word	Noun	Adjective	Verb	Adverb
water vapour	Yes	No	No	No
vapor	Yes	No	No	No

As nouns, vapor is a hypernym of water vapour; that is, vapor is a word with a broader meaning than water vapour:

water vapour: water in a vaporous form diffused in the atmosphere but below boiling temperature
vapor: a visible suspension in the air of particles of some substance

Other hypernyms of water vapour include vapour.

water vapour (noun)	vapor (noun)
water in a vaporous form diffused in the atmosphere but below boiling temperature	the process of becoming a vapor
	a visible suspension in the air of particles of some substance