gallows tree vs gallows

gallows tree and gallows both are nouns.

Word	Noun	Adjective	Verb	Adverb
gallows tree	Yes	No	No	No
gallows	Yes	No	No	No

As nouns, gallows is a hypernym of gallows tree; that is, gallows is a word with a broader meaning than gallows tree:

gallows tree: alternative terms for gallows
gallows: an instrument of execution consisting of a wooden frame from which a condemned person is executed by hanging

gallows tree (noun)	gallows (noun)
alternative terms for gallows	an instrument of execution consisting of a wooden frame from which a condemned person is executed by hanging