Define the following:
Amenorrhea

Explanation

**Step-by-Step Text Solution:**

1. **Definition of Amenorrhea**: Amenorrhea is defined as the absence of menstruation. It occurs when a woman’s menstrual cycle ceases during her reproductive years, which are typically from puberty to menopause.

2. **Reproductive Years**: The reproductive years of a female are the time frame from the onset of menstruation (puberty) until the cessation of menstruation (menopause). During this period, a woman is considered to be in her fertile years.

3. **Types of Amenorrhea**: There are two major types of amenorrhea:
- **Primary Amenorrhea**: This occurs when a female does not start menstruating by the age of puberty. In other words, if menstruation has not begun by the age of 16, it is classified as primary amenorrhea.
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