Quay/jetty/ pier/wharf

Wharfs are usually made primarily of wood, piers often use some concrete or cement, a jetty is often part of a main building, and a Quay (hope that's what you meant) is many times along river banks.

All these definitions are subject to interpretation and different resources will offer different variations as to what each one is. From a personal point I have been on structures known as piers which were primarily wood but had a cement flooring, I have also been on structures of the same name with wooden flooring and no cement anywhere on them.

If you ran across them in a single chapter within a book it may have been an author's way of using different words just to break up the monotony. Main thing, just think of them as places where boats are able to dock, or are moored. I also think there may be some verbiage associated with all of this according to the type of vessel. For example would an ocean liner or oil tanker have a jetty as their berth? Perhaps other variables such as loading capabilities would also be brought in. I realize this is not the best answering but it is my take on it, hope it has helped.

I think the others can be interchanged, but a jetty is a SHAPE. Its a (usually stone) pile of rip rap that juts out into the surf zone to artificially control the wave patterns.
A wharf and a pier and a quay, sort of do the same thing, they are areas where boats are loaded and unloaded. However, it seems that a pier may be roofed over ,

Where is our etymologist ?

Thanks a bunch!
It's a great help to me!