plum tree vs fruit tree

plum tree and fruit tree both are nouns.

Word	Noun	Adjective	Verb	Adverb
plum tree	Yes	No	No	No
fruit tree	Yes	No	No	No

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

plum tree: any of several trees producing edible oval fruit having a smooth skin and a single hard stone
fruit tree: tree bearing edible fruit

plum tree (noun)	fruit tree (noun)
any of several trees producing edible oval fruit having a smooth skin and a single hard stone	tree bearing edible fruit