vapor vs water vapour

vapor and water vapour both are nouns.

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

As nouns, water vapour is a hyponym of vapor; that is, water vapour is a word with a more specific, narrower meaning than vapor:

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

Other hyponyms of vapor include steam, water vapor.

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