vapour vs water vapour

vapour and water vapour both are nouns.

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

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

vapour: 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 vapour include steam, water vapor.

vapour (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