Absence of monthly regular bleeding.
Amenorrhea is a completely natural condition during pregnancy or breastfeeding. Outside this period, a distinction is made between primary amenorrhea, in which no menstrual bleeding has occurred beyond the age of 16. In secondary amenorrhea, a normal cycle was already present before the bleeding failed.
https://de.wikipedia.org/wiki/Amenorrhoe (Wikipedia CC-by-sa-3.0)