litchi vs litchi tree

litchi and litchi tree both are nouns.

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

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

litchi and litchi tree: Chinese tree cultivated especially in Philippines and India for its edible fruit; sometimes placed in genus Nephelium

Other synonyms of litchi include lichee, Litchi chinensis, Nephelium litchi.

litchi (noun)	litchi tree (noun)
Chinese fruit having a thin brittle shell enclosing a sweet jellylike pulp and a single seed; often dried	Chinese tree cultivated especially in Philippines and India for its edible fruit; sometimes placed in genus Nephelium
Chinese tree cultivated especially in Philippines and India for its edible fruit; sometimes placed in genus Nephelium