wharf vs quay

wharf and quay both are nouns.

Word	Noun	Adjective	Verb	Adverb
wharf	Yes	No	Yes	No
quay	Yes	No	No	No

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

wharf: a platform built out from the shore into the water and supported by piles; provides access to ships and boats
quay: wharf usually built parallel to the shoreline

Other hyponyms of wharf include levee.

wharf (noun)	quay (noun)
a platform built out from the shore into the water and supported by piles; provides access to ships and boats	wharf usually built parallel to the shoreline