vapor vs water vapor

vapor and water vapor both are nouns.

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

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

vapor: 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 vapor include steam, water vapour.

vapor (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