(1):
(n.) One that develops
(2):
(n.) A reagent used to produce an ingrain color by its action upon some substance on the fiber.
(3):
(n.) A chemical bath or reagent used in developing photographs.
(4):
(n.) A reagent by the action of which the latent image upon a photographic plate, after exposure in the camera, or otherwise, is developed and visible.
(5):
(n.) One who, or that which, develops.