hooks for fly tying

dry fly hooks are thin, nymph hooks are heavy wire.
wet flies can be tied on either hooks.
the heavier the wire the quicker it takes the fly down into the water column.
that's the best answer i can give ya.
 i take it when a pattern calls for a wet fly hook i'll use standard heavy wire nymph hook.

Also, the gap on a dry hook is usually much wider than on a nymph hook. Some manufactures make a dry/wet fly hook with heavier wire and a wider gap. These are great for traditional wets as well as over dressed dry's. I just bought some of the Mustad R50 Signiture hooks in this style and they are great for Humpy's tied for bluegill and small bass.
 
-J