It has only one line of symmetry (reflection symmetry). In non-technical usage, the term “semicircle” is sometimes used to refer to a half-disk, which is a two-dimensional geometric shape that also includes the diameter segment from one end of the arc to the other as well as all the interior points.

Can a circle be a 2D shape?

2-dimensional shapes are flat and only have two dimensions: length and width. They include squares, rectangles, circles, triangles, and more. Read on to learn all about 2D shapes and the differences between 2D and 3D shapes.

What is a 2D shape?

2D shapes have sides and corners, and are completely flat. Watch the video to learn all about 2D shapes, like circles, triangles, squares, rectangles, pentagons, hexagons and octagons!

A closed shape consisting of half a circle and a diameter of that circle*. A semicircle is a half circle, formed by cutting a whole circle along a diameter line, as shown above. Any diameter of a circle cuts it into two equal semicircles. * An alternative definition is that it is an open arc.