vapour vs water vapor

vapour and water vapor both are nouns.

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

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

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

Other hyponyms of vapour include steam, water vapour.

vapour (noun)	water vapor (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