tea napkin vs serviette

tea napkin and serviette both are nouns.

Word	Noun	Adjective	Verb	Adverb
tea napkin	Yes	No	No	No
serviette	Yes	No	No	No

As nouns, serviette is a hypernym of tea napkin; that is, serviette is a word with a broader meaning than tea napkin:

tea napkin: a small napkin used when tea is served
serviette: a small piece of table linen that is used to wipe the mouth and to cover the lap in order to protect clothing

Other hypernyms of tea napkin include napkin, table napkin.

tea napkin (noun)	serviette (noun)
a small napkin used when tea is served	a small piece of table linen that is used to wipe the mouth and to cover the lap in order to protect clothing