endocarp vs peach pit

endocarp and peach pit both are nouns.

Word	Noun	Adjective	Verb	Adverb
endocarp	Yes	No	No	No
peach pit	Yes	No	No	No

As nouns, peach pit is a hyponym of endocarp; that is, peach pit is a word with a more specific, narrower meaning than endocarp:

endocarp: the hard inner (usually woody) layer of the pericarp of some fruits (as peaches or plums or cherries or olives) that contains the seed
peach pit: the stone seed of a peach

Other hyponyms of endocarp include cherry stone.

endocarp (noun)	peach pit (noun)
the hard inner (usually woody) layer of the pericarp of some fruits (as peaches or plums or cherries or olives) that contains the seed	the stone seed of a peach