Four words have been given, out of which three are alike in some manner and one is different. Select the odd one.

Larva Foal Nymph Stag

Stag

Larva ⇒ A larva is  the young stage of some insects. Foal  ⇒ The young one of a horse is called foal Nymph ⇒ A larva is  the young stage of some kind of invertebrates. Stag ⇒ A male deer is called stag