nitty-gritty vs essence

nitty-gritty and essence both are nouns.

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

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

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

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

nitty-gritty (noun)	essence (noun)
the choicest or most essential or most vital part of some idea or experience	a toiletry that emits and diffuses a fragrant odor
	the choicest or most essential or most vital part of some idea or experience
	the central meaning or theme of a speech or literary work
	any substance possessing to a high degree the predominant properties of a plant or drug or other natural product from which it is extracted