-pə(r) noun
( -s )
1. : a person who develops something especially habitually or as an occupation: as
a. : a worker who develops photographic materials (as films and prints)
b. : a person who develops real estate ; often : one that improves and subdivides land and builds and sells residential structures thereon
2. : something that develops or is used in developing: as
a. : a chemical agent used to produce a dye by reaction with a dye or dye intermediate on the fiber — see dye table I
b. : a chemical bath or reagent used in developing exposed photographic materials