Definition

1. Noun:
   • A state or period of heightened sexual arousal and activity in nonhuman mammals: This is the primary biological and zoological meaning, referring to the recurring period of fertility and sexual receptivity in female mammals, often marked by specific physiological and behavioral changes. Commonly known as "heat."
   • [Capitalized, as Oestrus] The type genus of the family Oestridae: In zoological taxonomy, Oestrus is the genus that includes species like the sheep botfly (Oestrus ovis).

Examples of Usage

• Noun (Physiological State):
  • The female dog is in oestrus and will attract males from the neighborhood.
  • Researchers monitored the oestrus cycles of the mice in the laboratory.
• Noun (Taxonomic Genus):
  • The parasite Oestrus ovis is a cause of myiasis in sheep.

Advanced Usage

• "To come into oestrus": To enter the state of sexual receptivity.
  • The herd's females typically come into oestrus during the spring season.
• "Oestrus cycle": The recurring physiological changes that are regulated by reproductive hormones in nonhuman mammals.
  • The study focused on the hormonal regulation of the oestrus cycle.

Variants and Related Words

• Estrus: The American English spelling of .
• Oestrous (adj): Pertaining to or involving oestrus.
  • Oestrous behavior was observed.
• Dioestrus/Diestrus (n): The period of sexual inactivity between cycles of oestrus.
• Oestrogen/Estrogen (n): A primary female sex hormone involved in regulating the oestrus cycle and other functions.

Synonyms

• Heat: The common, non-technical term for oestrus.
• Rut: While typically refers to the mating period and associated behavior in male mammals (like deer), it is sometimes used more broadly in the context of mating seasons.

Notes on Meaning and Usage

• The word oestrus is specifically used in the context of nonhuman mammals. For humans, the equivalent phase of the menstrual cycle is typically referred to as the fertile period or ovulation, not oestrus.
• The spelling oestrus is common in British English, while estrus is standard in American English. The initial 'o' is often silent in pronunciation (/ˈiːstrəs/ or /ˈɛstrəs/).
• In general biological and veterinary contexts, the term is neutral and scientific. In casual conversation about pets or livestock, the word heat is far more common.

Noun

1. type genus of the Oestridae: sheep botflies
2. applies to nonhuman mammals: a state or period of heightened sexual arousal and activity