3D (or 3-D ) means three-dimensional, or having three dimensions . For example, a box is three-dimensional; it is solid , and not thin like a piece of paper . It has volume , a top and bottom, left and right ( sides ), as well as a front and back. You can turn the box around to view it from another side (called a face, surface or simply side ).

A dimension can be measured in inches , microns , miles , kilometers , or any other unit of length .

The three dimensions are often called length (or depth), width (or breadth), and height . Some purposes use other words.

3D graphics are used to make video games or animated movies . Many calculations are needed to make pictures seem three-dimensional on a screen. Modern computers usually have a GPU ( Graphics Processing Unit ) to handle these calculations.

Binocular vision helps people to see the third dimension easily.