sour vs acidity

sour and acidity both are nouns.

Word	Noun	Adjective	Verb	Adverb
sour	Yes	Yes	Yes	No
acidity	Yes	No	No	No

As nouns, sour and acidity are synonyms defined as:

Other synonyms of sour include sourness.

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

sour: the taste experience when vinegar or lemon juice is taken into the mouth
acidity: the taste experience when something acidic is taken into the mouth

Other hyponyms of sour include acidulousness.

sour (noun)	acidity (noun)
the property of being acidic	pH values below 7
the taste experience when vinegar or lemon juice is taken into the mouth	the property of being acidic
a cocktail made of a liquor (especially whiskey or gin) mixed with lemon or lime juice and sugar	the taste experience when something acidic is taken into the mouth

sour (adjective)	acidity (adjective)
having a sharp biting taste
showing a brooding ill humor
inaccurate in pitch
smelling of fermentation or staleness
in an unpalatable state
one of the four basic taste sensations; like the taste of vinegar or lemons

sour (verb)	acidity (verb)
go sour or spoil
make sour or more sour