ship's boat vs pinnace

ship's boat and pinnace both are nouns.

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

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

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

Other synonyms of ship's boat include cutter, tender.

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