pistachio vs nut tree

pistachio and nut tree both are nouns.

Word	Noun	Adjective	Verb	Adverb
pistachio	Yes	No	No	No
nut tree	Yes	No	No	No

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

pistachio: small tree of southern Europe and Asia Minor bearing small hard-shelled nuts
nut tree: tree bearing edible nuts

pistachio (noun)	nut tree (noun)
nut of Mediterranean trees having an edible green kernel	tree bearing edible nuts
small tree of southern Europe and Asia Minor bearing small hard-shelled nuts