mast vs topmast

mast and topmast both are nouns.

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

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

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

mast (noun)	topmast (noun)
a vertical spar for supporting sails	the mast next above a lower mast and topmost in a fore-and-aft rig
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