pourboire vs gratuity

pourboire and gratuity both are nouns.

Word	Noun	Adjective	Verb	Adverb
pourboire	Yes	No	No	No
gratuity	Yes	No	No	No

As nouns, pourboire and gratuity are synonyms defined as:

pourboire and gratuity: a relatively small amount of money given for services rendered (as by a waiter)

Other synonyms of pourboire include backsheesh, baksheesh, bakshis, bakshish, tip.

pourboire (noun)	gratuity (noun)
a relatively small amount of money given for services rendered (as by a waiter)	a relatively small amount of money given for services rendered (as by a waiter)
	an award (as for meritorious service) given without claim or obligation