litchi vs lychee

litchi and lychee both are nouns.

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

As nouns, litchi and lychee are synonyms defined as:

litchi and lychee: Chinese fruit having a thin brittle shell enclosing a sweet jellylike pulp and a single seed; often dried

Other synonyms of litchi include leechee, lichee, lichi, litchee, litchi nut.

litchi (noun)	lychee (noun)
Chinese fruit having a thin brittle shell enclosing a sweet jellylike pulp and a single seed; often dried	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