vapour vs clouding up

vapour and clouding up both are nouns.

Word	Noun	Adjective	Verb	Adverb
vapour	Yes	No	No	No
clouding up	Yes	No	No	No

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

Other hyponyms of vapour include boiling, clouding, smoke, smoking.

vapour (noun)	clouding up (noun)
the process of becoming a vapor	the process whereby water particles become visible in the sky
a visible suspension in the air of particles of some substance