A semicircle is simply half of a circle : imagine cutting a perfect circle exactly along its diameter so you get two equal “half‑moon” shapes.

What does “semicircle” mean?

  • In geometry, a semicircle is the shape you get when a circle is divided into two equal parts by a straight line through its center (the diameter).
  • The curved part of a semicircle is an arc that measures 180∘180^\circ 180∘, which is half of a full circle’s 360∘360^\circ 360∘.
  • In everyday language, “semicircle” can also mean any arrangement in a half‑circle shape, like chairs set in a semicircle around a stage or tents set in a semicircle around a campfire.

Quick geometry facts (mini‑guide)

  • Half a circle: A semicircle is half the circumference and half the area of a full circle (if you include the flat diameter edge as part of the boundary).
  • Angle of the arc: The curved edge spans 180 degrees, or π\pi π radians.
  • Symmetry: A semicircle has one line of reflection symmetry along the diameter.

A simple way to picture it: fold a round piece of paper exactly in half—when you crease and cut along the fold, each piece you get is a semicircle.

Where you see semicircles in real life

  • A standard protractor (the one used to measure angles) is shaped like a semicircle.
  • Many speedometers and gauges on dashboards follow a semicircular arc.
  • Some foods (like folded tacos or half a pita) often look roughly semicircular when cut or folded.

Short answer (TL;DR)

A semicircle is the shape formed by half of a circle , including the 180° curved edge and usually the straight line (diameter) that cuts the circle in two.

Information gathered from public forums or data available on the internet and portrayed here.