medlar tree vs fruit tree

medlar tree and fruit tree both are nouns.

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

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

medlar tree: small deciduous Eurasian tree cultivated for its fruit that resemble crab apples
fruit tree: tree bearing edible fruit

medlar tree (noun)	fruit tree (noun)
small deciduous Eurasian tree cultivated for its fruit that resemble crab apples	tree bearing edible fruit