Base (geometry) facts for kids

A cube is made of six squares; the square is therefore the base of the cube.

In flat geometry, the base is usually the side a polygon sits on. Think of it as the bottom side of a shape, which is used as a reference for other measurements. For shapes like a triangle or a quadrilateral (a four-sided shape), the base is often labeled as b. It's super important for figuring out the area of these shapes, like triangles and parallelograms.

Many geometric shapes that have more than two dimensions (like solids) are built using flat, two-dimensional shapes. For example, a tetrahedron is made from four triangles, and a cube is built from six squares. In these cases, the flat shape used to build the solid is called the base. So, the triangle is the base of the tetrahedron, and the square is the base of the cube.

However, some 3D shapes are built using different kinds of flat shapes. For instance, a pyramid uses one rectangle and four triangles. Here, the rectangle is considered the base of the pyramid. A cylinder uses a circle or an ellipse as its base.

Related pages

• Altitude

Images for kids

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  A skeletal pyramid with its base highlighted

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  The altitude from A intersects the extended base at D (a point outside the triangle).

See also

In Spanish: Base (geometría) para niños