topgallant sail vs topgallant

topgallant sail and topgallant both are nouns.

Word	Noun	Adjective	Verb	Adverb
topgallant sail	Yes	No	No	No
topgallant	Yes	No	No	No

As nouns, topgallant sail and topgallant are synonyms defined as:

topgallant sail and topgallant: a sail set on a yard of a topgallant mast

topgallant sail (noun)	topgallant (noun)
a sail set on a yard of a topgallant mast	a mast fixed to the head of a topmast on a square-rigged vessel
	a sail set on a yard of a topgallant mast