mast vs mainmast

mast and mainmast both are nouns.

Word	Noun	Adjective	Verb	Adverb
mast	Yes	No	No	No
mainmast	Yes	No	No	No

As nouns, mainmast is a hyponym of mast; that is, mainmast is a word with a more specific, narrower meaning than mast:

Other hyponyms of mast include foremast, jigger, jiggermast, jury mast, mizen, mizenmast, mizzen, mizzenmast, topmast.

mast (noun)	mainmast (noun)
a vertical spar for supporting sails	the chief mast of a sailing vessel with two or more masts
any sturdy upright pole
nuts of forest trees used as feed for swine
nuts of forest trees (as beechnuts and acorns) accumulated on the ground