A penis (plural penises or penes /-/) is the main sexual organ of most male animals. It is used to inseminate females (or hermaphrodites) during sex (copulation). In some animals, the penis is also be used to urinate.
Penises are found in many animal species. 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.
- Janet Leonard; Alex Cordoba-Aguilar R (18 June 2010). The Evolution of Primary Sexual Characters in Animals. Oxford University Press. ISBN 978-0-19-971703-3. Retrieved 20 July 2013.