Crab is an ambiguous vernacular name used in French to refer to many species of decapod crustaceans , most of them edible.

There are two infra-orders of crabs, depending on the characteristics of their abdomen: Brachyura , or true crabs, and Paguroidea ( coconut crabs, king crabs ). However, all the species of these infra-orders are not spontaneously qualified as crab, for example the species called spider crabs among the Brachyura or even the hermit crabs , among the Paguroidea.