quintessence vs nitty-gritty

quintessence and nitty-gritty both are nouns.

Word	Noun	Adjective	Verb	Adverb
quintessence	Yes	No	No	No
nitty-gritty	Yes	No	No	No

As nouns, nitty-gritty is a hypernym of quintessence; that is, nitty-gritty is a word with a broader meaning than quintessence:

quintessence: the purest and most concentrated essence of something
nitty-gritty: the choicest or most essential or most vital part of some idea or experience

Other hypernyms of quintessence include center, centre, core, essence, gist, heart, heart and soul, inwardness, kernel, marrow, meat, nub, pith, substance, sum.

quintessence (noun)	nitty-gritty (noun)
the purest and most concentrated essence of something	the choicest or most essential or most vital part of some idea or experience
the most typical example or representative of a type
the fifth and highest element after air and earth and fire and water; was believed to be the substance composing all heavenly bodies