Definition: Early menopause, according to the North American Menopause Society is menopause that occurs well before the usual age of menopause, or 51 years. Some sources designate the age of forty-five as the cutoff, and label any menopause occurring prior to forty-five as "early."
Early menopause is a little different from "premature menopause" in that premature menopause is one that occurs prior to the age of forty. This is also called "premature ovarian failure." Early menopause may occur naturally, or it may be induced by surgery removing or damaging the ovaries, or by medical treatments like chemotherapy.