estrus
UK[ˈɛstrəs]US[ˈɛstrəs]
n
A recurring period of sexual receptivity and fertility in many female mammals; heat.
Etymology
The word 'estrus' entered English in the late 19th century from the Latin 'oestrus', which meant 'gadfly, frenzy, or sting'. This Latin term was itself a borrowing from the Greek 'oistros', carrying the same dual sense of a stinging insect and a mad impulse. The semantic evolution from a literal sting or frenzy to the specific biological state is metaphorical, likening the intense, driving physiological impulse of fertility to a maddening sting or frenzy. This Greek root can be traced further back to the Proto-Indo-European base eis-, meaning 'to move violently', which connects to the agitated behavior associated with this reproductive phase.
Analysis
The word is a simplex loanword from Latin. It is not productively segmented in modern English spelling.
Examples
The female cat will only allow mating when she is in estrus.
Scientists monitor hormone levels to predict the onset of estrus in livestock.
The estrus cycle varies in length between different mammalian species.