medlar vs fruit tree

medlar and fruit tree both are nouns.

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

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

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

medlar (noun)	fruit tree (noun)
crabapple-like fruit used for preserves	tree bearing edible fruit
a South African globular fruit with brown leathery skin and pithy flesh having a sweet-acid taste
small deciduous Eurasian tree cultivated for its fruit that resemble crab apples
small deciduous tree of southern Africa having edible fruit