The absence of a period for a consecutive 12 months
defined as amenorrhea (period free) for 12 consecutive months in a woman with a uterus after the final menstrual period (FMP)
not in the Learning outcome but here are some other definitions

puberty occurs in females at an average age of 12years 11months (in uk)
this means menstration occurs once per month for females at reproductive age until they are about 52yrs
(some people can get premenopause and end up with menopuase at aged 40 etc)
the next phase is perimenopause which usually. lasts 3-4yrs
the menstrual cycle become irregular, sometimes no ovulation occurs.
start to experience symptoms of menopause.
Late perimenpause
periods become few months apart
menopause symptoms worsen