T-shirt vs tee shirt

T-shirt and tee shirt both are nouns.

Word	Noun	Adjective	Verb	Adverb
T-shirt	Yes	No	No	No
tee shirt	Yes	No	No	No

As nouns, T-shirt and tee shirt are synonyms defined as:

Other synonyms of T-shirt include jersey.

T-shirt (noun)	tee shirt (noun)
a close-fitting pullover shirt	a close-fitting pullover shirt