tartness vs sour

tartness and sour both are nouns.

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

As nouns, sour is a hypernym of tartness; that is, sour is a word with a broader meaning than tartness:

Other hypernyms of tartness include acidity, sourness.

As nouns, tartness and sour are synonyms defined as:

tartness and sour: the taste experience when vinegar or lemon juice is taken into the mouth

Other synonyms of tartness include sourness.

tartness (noun)	sour (noun)
a sharp sour taste	the property of being acidic
a rough and bitter manner	the taste experience when vinegar or lemon juice is taken into the mouth
the taste experience when vinegar or lemon juice is taken into the mouth	a cocktail made of a liquor (especially whiskey or gin) mixed with lemon or lime juice and sugar

tartness (adjective)	sour (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

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