What does "menarche" mean?

The onset of menstruation; a girl's first period.

How do you pronounce "menarche"?

Pronounced //ˈmɛˌnɑɹ.ki//.

Common synonyms include: age at menarche, first menstrual period, initial menses, menarcheal age, onset of menses, timing of menarche.

/ˈmɛˌnɑɹ.ki/ noun

noun ·Rare ·Advanced level

Noun

1
The onset of menstruation; a girl's first period.
"How old is she? Nine? Ten? The menarche is not far off – a hint of a bosom, poor child."
2
the first occurrence of menstruation in a woman wordnet

"Menopause is the opposite of menarche."

First attested 1900, from German Menarche, formed from meno- + -arche.