The first menstrual period, usually occurring during puberty.(noun)
American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Use "menarche" in a sentence
"Could it be that earlier menarche is actually more normal than later menarche?"
"And he's right: though they can be affected by such factors as weight, physical activity, and environmental toxins, the average age of menarche is around twelve and a half, and the average age of spermarche is around fourteen."
"A new study suggests that the earlier a woman reached this milestone of puberty, called menarche, the slightly faster her kids will grow."