Amenorrhea means not having a menstrual period.
Amenorrhea is either primary or secondary.
Primary amenorrhea is not having menstrual periods by the age of 16. Secondary amenorrhea is the absence of periods in a woman who had regular menstrual periods previously. An abnormality of any of the above may keep you from having a period. The main cause of primary amenorrhea is late puberty without any permanent abnormality. This delay in most cases occurs for no known reason.