Faces, edges, vertices

Solids (3D shapes) have three kinds of parts — all three are worth remembering:

• Face — a flat part of the solid. For example, one "side" of a cube.
• Edge — a straight line where two faces meet.
• Vertex — a corner where three (or more) edges meet.

Cube

The cube is a solid where all faces are the same square.

• 6 faces (six squares)
• 12 edges
• 8 vertices

Picture a dice or a sugar cube. Count the sides — you get 6.

Cuboid

A cuboid (rectangular box) looks like a cube but its faces are rectangles (which can be different sizes).

• 6 faces, 12 edges, 8 vertices — exactly like the cube.

Classic example: a shoebox or a book.

Pyramid

A pyramid has a base (for example, a square) and all the other faces are triangles that meet at one vertex at the top.

• 5 faces (1 square + 4 triangles)
• 8 edges
• 5 vertices (4 below, 1 on top)

The most famous pyramid: an Egyptian pyramid.

Cylinder

A cylinder has two round faces (top and bottom) and one curved face around it.

• 3 faces (2 circles + 1 curved)
• 2 edges (circles, top and bottom)
• 0 vertices

Classic example: a tin can, a piece of salami.

Tricks for counting

• Count faces by going "all around the solid". First the top, then all the sides, finally the bottom.
• Edges are "lines you could trace with a pen". They are where two faces meet.
• Vertices are the corners. Where three (or more) edges come together.

Summary

• Face = flat part. Edge = line between two faces. Vertex = corner.
• Cube: 6 faces, 12 edges, 8 vertices.
• Cuboid: the same as a cube.
• Pyramid (with a 4-sided base): 5 faces, 8 edges, 5 vertices.
• Cylinder: 3 faces, 2 edges, 0 vertices.