Etymology

Noun

1. The onset of menstruation; the beginning of the menstrual period. A girl's first period.
   • 1973, Patrick O'Brian, HMS Surprise:

     How old is she? Nine? Ten? The menarche is not far off – a hint of a bosom, poor child.

   • 1978, Benjamin Walker, Encyclopedia of Metaphysical Medicine, Routledge 1978, p. 252:

     The most potent and indeed dangerous of all menstrual blood was the menarche, the first day's flow of the first menstruation of a virgin girl.