hypostasis vs nitty-gritty

hypostasis and nitty-gritty both are nouns.

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

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

hypostasis: (metaphysics) essential nature or underlying reality
nitty-gritty: the choicest or most essential or most vital part of some idea or experience

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

hypostasis (noun)	nitty-gritty (noun)
(metaphysics) essential nature or underlying reality	the choicest or most essential or most vital part of some idea or experience
any of the three persons of the Godhead constituting the Trinity especially the person of Christ in which divine and human natures are united
the accumulation of blood in an organ
the suppression of a gene by the effect of an unrelated gene