Botanically pumpkin is

Botanically Pumpkin is Pepo.
Pepo is a Berry with a hard, thick, and fleshy rind, multi-seeded fruit. It is a typical fruit of the gourd family, (Cucurbitaceae). E.g. watermelon, cucumber, squash, cantelope and pumpkin.
A pumpkin is a cultivar of winter squash that is round with smooth, slightly ribbed skin and is most often deep yellow to orange in coloration. The thick shell contains seeds and pulp.