nitty-gritty vs pith

nitty-gritty and pith both are nouns.

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

As nouns, nitty-gritty and pith are synonyms defined as:

nitty-gritty and pith: the choicest or most essential or most vital part of some idea or experience

Other synonyms of nitty-gritty include center, centre, core, essence, gist, heart, heart and soul, inwardness, kernel, marrow, meat, nub, substance, sum.

nitty-gritty (noun)	pith (noun)
the choicest or most essential or most vital part of some idea or experience	the choicest or most essential or most vital part of some idea or experience
	soft spongelike central cylinder of the stems of most flowering plants

nitty-gritty (verb)	pith (verb)
	remove the pith from (a plant)