waiter vs sommelier

waiter and sommelier both are nouns.

Word	Noun	Adjective	Verb	Adverb
waiter	Yes	No	No	No
sommelier	Yes	No	No	No

As nouns, sommelier is a hyponym of waiter; that is, sommelier is a word with a more specific, narrower meaning than waiter:

Other hyponyms of waiter include carhop, counterperson, wine steward, wine waiter, waitress.

waiter (noun)	sommelier (noun)
a person whose occupation is to serve at table (as in a restaurant)	a waiter who manages wine service in a hotel or restaurant
a person who waits or awaits