Dictionary.com
definitions

men-

  1. variant of meno- before a vowel: menarche.
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018
men- in Medicine

men-

pref.
  1. Variant ofmeno-
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.