A nymph is the juvenile form of some invertebrates, particularly insects, which undergoes gradual metamorphosis (hemimetabolism) before reaching its adult stage

Unlike a typical larva, a nymph's overall form already resembles that of the adult, except for a lack of wings (in winged species) and the emergence of genitalia. In addition, while a nymph moults, it never enters a pupal stage. Instead, the final moult results in an adult insect. Nymphs undergo multiple stages of development called instars.