sneaker vs tennis shoe

sneaker and tennis shoe both are nouns.

Word	Noun	Adjective	Verb	Adverb
sneaker	Yes	No	No	No
tennis shoe	Yes	No	No	No

As nouns, sneaker and tennis shoe are synonyms defined as:

Other synonyms of sneaker include gym shoe.

sneaker (noun)	tennis shoe (noun)
a canvas shoe with a pliable rubber sole	a canvas shoe with a pliable rubber sole
someone acting as an informer or decoy for the police