Menstruation is the monthly bleeding in girls and women when the inner lining of the uterus breaks down and comes out through the vagina; it usually begins at puberty and repeats in a cycle.

Simple definition (Class 8 level)

  • Menstruation is the monthly shedding of the inner lining of the uterus (womb).
  • During this process, blood and tissue flow out of the uterus through the vagina for about 3–7 days.
  • It usually starts in girls during adolescence (puberty) and continues until about 45–50 years of age.

How it happens (in short)

  • Every month, the uterus prepares a soft, thick lining to receive a fertilised egg and grow a baby.
  • If no fertilisation and pregnancy occur, this lining is not needed and breaks down.
  • The broken lining, along with blood, comes out of the body as menstrual flow; this is called menstruation.

Key points for exams (Class 8)

  • Menstruation is the monthly breakdown and bleeding of the uterine lining in females.
  • It occurs in a regular cycle of about 28–30 days (may vary from person to person).
  • It starts at puberty and stops around 45–50 years (menopause).

Very short exam-style answer

  • “Menstruation is the monthly process in which the thickened lining of the uterus, along with blood, breaks down and flows out through the vagina in females.”

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