Dioecy (Greek: "two households"; adjective form: dioecious) is a characteristic of a species, meaning that it has distinct male and female individual organisms or colonies, meaning that a colony contains only either male or female individuals. Dioecious reproduction is biparental reproduction.

In zoology

In zoology, dioecious species may be opposed to hermaphroditic species, meaning that an individual is of only one sex, in which case the synonym gonochory is more often used. Dioecy may also describe colonies, such as the colonies of Siphonophorae, which may be either dioecious within a species or monoecious. Dioecious colonies contain members of only one sex, whereas monoecious colonies contain members of both sexes.

Most animal species are dioecious (gonochoric).

In botany

Dioecious species have the male and female reproductive structures on separate plants. The meaning of male and female in the context of plants is different from that used in animal groups and the usage is not strictly correct. This issue is discussed below in the Alternation of generations section. About 6 percent of angiosperm species are entirely dioecious and about 7% of angiosperm genera contain some dioecious species. Examples of dioecious plant species include ginkgos, willows, cannabis and African teak. More examples of dioecious plants can be found in the Wikipedia category, Dioecious plants.