seed vessel vs exocarp

seed vessel and exocarp both are nouns.

Word	Noun	Adjective	Verb	Adverb
seed vessel	Yes	No	No	No
exocarp	Yes	No	No	No

As nouns, exocarp is a hyponym of seed vessel; that is, exocarp is a word with a more specific, narrower meaning than seed vessel:

seed vessel: the ripened and variously modified walls of a plant ovary
exocarp: outermost layer of the pericarp of fruits as the skin of a peach or grape

Other hyponyms of seed vessel include epicarp, mesocarp, endocarp, pit, stone, capsule, bur, burr.

seed vessel (noun)	exocarp (noun)
the ripened and variously modified walls of a plant ovary	outermost layer of the pericarp of fruits as the skin of a peach or grape