In Geometry we can have different dimensions.

The number of dimensions is how many values are needed to locate points on a shape.

dimensions 0, 1, 2 and 3

Point, Line, Plane and Solid

A Point has no dimensions, only position
A Line is one-dimensional
A Plane is two dimensional (2D)
A Solid is three-dimensional (3D)


0 dimensions

Let us start with a point. A point has no dimensions.

A point really has no size at all! But we show them as dots so we can see where they are.

1 dimension

Now let's allow the point to move in one direction. We get a line.

We need just one value to find a point on that line. So we have one dimension. A line is one-dimensional.

2 dimensions

Now lets allow the point to move in a different direction. And we get a plane. We need two values to find a point on that plane. So we have two dimensions, or "2D".

Circles, triangles, squares and more are plane shapes.

3 dimensions Now we let that point move in another completely different direction and we have three dimensions.

Spheres, cubes, cylinders and more are 3-dimensional or "3D". We also call them solid shapes.

The world we live in is 3D.

4 dimensions
Tessaract, a 4D shape
In mathematics we can have more dimensions, but they are hard to draw!