pinnace vs ship's boat

pinnace and ship's boat both are nouns.

Word	Noun	Adjective	Verb	Adverb
pinnace	Yes	No	No	No
ship's boat	Yes	No	No	No

As nouns, pinnace and ship's boat are synonyms defined as:

pinnace and ship's boat: a boat for communication between ship and shore

Other synonyms of pinnace include cutter, tender.

pinnace (noun)	ship's boat (noun)
a boat for communication between ship and shore	a boat for communication between ship and shore