Menopause is a natural biological process that marks the end of a womans menstrual cycles. It is defined as the point in time when a woman has gone 12 consecutive months without a menstrual period. The years leading up to menopause, when women may have changes in their monthly cycles, hot flashes, or other symptoms, are called the menopausal transition or perimenopause. The menopausal transition most often begins between ages 45 and 55, but it can start as early as the mid-30s or as late as the 60s. The duration of the menopausal transition can vary, lasting about seven years on average but can be as long as 14 years. The duration can depend on lifestyle factors such as smoking, age it begins, and race and ethnicity. The average age for menopause is around 51 in the United States. However, some women experience menopause in their 40s, while others may not reach menopause until their 60s. It is not possible to predict when an individual woman will experience menopause, although there are associations between the age at menopause and certain demographic, health, and genetic factors.