There are three main *terms* you need to know
when you’re talking about solid, 3D shapes. The terms are *edge*, *corner/vertex*
and *face*. This diagram shows what each one of these is:

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A *face* is a flat surface on a solid shape.
It has to be flat to count as a face. The surface of a sphere for instance
doesn’t count as a face because it is curved. A face is a two dimensional
shape – it has an area. Sometimes they’re called *sides* instead of
faces.

An *edge* means exactly the same as when we
use it in everyday life, such as to describe the edge of a table. Edges are
the straight line bits *between* faces on a solid shape. Edges have to be
*straight* to count as edges. An edge is a one dimensional line – it only
has a length.

*Corners *are the pointy bits on a solid
shape. They are one dimensional points – they don’t have any length or area.
They are also called *vertices* (singular form ‘vertex’).