tartness vs sourness

tartness and sourness both are nouns.

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

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

Other hypernyms of tartness include acidity, sour.

As nouns, tartness and sourness are synonyms defined as:

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

Other synonyms of tartness include sour.

tartness (noun)	sourness (noun)
a sharp sour taste	the property of being acidic
a rough and bitter manner	a sullen moody resentful disposition
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