Penis

A penis (from Latin: penis; plural penises or penes /-niːz/) is the main sexual organ of most male animals. It is used to inseminate females (or hermaphrodites) during sex (copulation).^[1] In some animals, the penis is also used to urinate.

This article is about penises of animals in general. For the human organ, see human penis.

The penis of an Asian elephant

Penises are found in many animal species, mainly warm-blooded mammals. They are found in both vertebrates and invertebrates. Penises are not found in every species of animal. In those species where the male does have a penis, the penises are not homologous. This means that it evolved separately in each species. They also fill with blood so it can fit in the women’s vagina, in a process called ‘erecting’. During sleep, the human penis may have more blood in it than usual, the term for this is called “morning wood”. Once erect, the penis can eject semen through ejaculation.