The estrus cycle (also oestrus cycle; derived from Latin oestrus and originally from Greek οἶστρος meaning sexual desire) comprises the recurring physiologic changes that are induced by reproductive hormones in most mammalian therian females. Estrus cycles start after sexual maturity in females and are interrupted by anestrous phases or pregnancies. Typically, estrus cycles continue until death. Some animals may display bloody vaginal discharge, often mistaken for menstruation, also called a "period".