Shape

A shape is a graphical representation of an object's form or its outer edge. It helps us understand how something looks, separate from other features like color, texture, or what it’s made of. In geometry, when we talk about shape, we ignore where the object is, how big it is, how it’s turned, or whether it’s a mirror image.

A plane shape stays flat, like on a piece of paper, while a solid shape has depth, like a ball or a cube. We call these two-dimensional shapes or 2D shapes when they’re flat, and three-dimensional shapes or 3D shapes when they have height, width, and depth. Shapes are important in art, design, and many areas of science and math.

Classification of simple shapes

Main article: Lists of shapes

Simple shapes can be grouped into big families. For example, polygons are shapes made of straight lines and are named based on how many sides they have, like triangles and quadrilaterals. Triangles can be further described as equilateral, isosceles, or scalene, while quadrilaterals can be rectangles, rhombi, or squares.

Other common shapes include points, lines, flat surfaces called planes, and curved shapes like ellipses, circles, and parabolas. In three dimensions, familiar shapes are polyhedra with flat faces, egg-like ellipsoids, round cylinders, and cone-shaped cones.

We often use these shapes to describe everyday objects. For example, a manhole cover is usually described as having the shape of a disk because it looks almost exactly like a flat, round circle.

In geometry

A geometric shape is what remains when we ignore where an object is, how big it is, how it is turned, or whether it is a mirror image. This means that if you move, resize, rotate, or flip a shape, it is still considered the same shape.

Two-dimensional shapes, like triangles, squares, and pentagons, are made from points connected by lines. Other two-dimensional shapes can be bounded by curves, such as circles or ellipses. Three-dimensional shapes, like cubes and pyramids, are made from points, lines, and flat surfaces. Other three-dimensional shapes can be bounded by curved surfaces, such as spheres.

Equivalence of shapes

In geometry, two things have the same shape if you can change one into the other by moving it, turning it, or changing its size. This means the shape is all the information about an object that stays the same no matter where it is, how big it is, or which way it faces.

For example, the letters "d" and "p" have the same shape because you can move the "d" to the right, turn it upside down, and make it bigger to look just like a "p". But a "b" and a "p" have different shapes because you can't make them look the same by just moving or turning them. Also, a right hand and a left hand have different shapes even though one is just a mirror image of the other.

Human perception of shapes

People see the world using many different shapes. Some scientists think our brains break things down into simple shapes like cones and spheres. Others believe we look at features such as how shapes can be split apart, how round or pointy they are.

The way something looks, like if its edges are sharp or smooth, can change how people feel about it. For example, rounded shapes on product packaging often make people think of softness, while angular shapes might feel harder. Shapes also help guide where people look and focus their attention.