tree vs tree diagram

tree and tree diagram both are nouns.

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

As nouns, tree and tree diagram are synonyms defined as:

tree (noun)	tree diagram (noun)
a tall perennial woody plant having a main trunk and branches forming a distinct elevated crown; includes both gymnosperms and angiosperms	a figure that branches from a single root
a figure that branches from a single root

tree (verb)	tree diagram (verb)
stretch (a shoe) on a shoetree
chase an animal up a tree
plant with trees
force a person or an animal into a position from which he cannot escape