Art,
The definitions that I once heard, a long time ago, didn't differentiate between soundbox materials.

Lute. has strings parallel with the soundbox and has a long neck. (includes guitar and banjo)

Fiddle. has strings parallel with the soundbox and has a short neck.

Zither. has strings parallel with the soundbox and no neck. (includes autoharp, the hammered dulcimers, piano, etc.)

Harp. has strings at 90 degrees to the soundbox.

That's all I can remember for now, I sure we have some students out there who know more.

Bert.