Simple definition
Menopause is the point when you have gone 12 consecutive months without a menstrual period (and there is no other cause, such as pregnancy or certain medications). After that milestone, you are considered postmenopausal.
Perimenopause is the transition leading up to that final period. Hormone levels fluctuate, cycles often become irregular, and symptoms like hot flashes or sleep changes are common - sometimes for years.
Educational summary only; your clinician confirms timing based on your history and exam.