## Summary

Three dimensional objects or solids generally have length, breadth and height. Three dimensional objects look different from different locations or angles.

**Polyhedron**

A polyhedron is a solid shape bounded by polygons whereas non-polyhedrons do not have polygon shaped faces.

**Faces**

Polygons forming a polyhedron are known as its faces.

**Edges**

Line segments common to intersecting faces of a polyhedron

**are known as its edges.**

**Vertices**

Points of intersection of edges of a polyhedron are known as its vertices.

**Reguler polyhedron**

A polyhedron is said to be regular if its faces are made up of regular polygons and the same number of faces meet at each vertex.

**Irregular polyhedron**

An irregular polyhedron is made of polygons whose sides and angles are not of equal measure.

F + V = E + 2 is known as Euler’s formula and it holds true for any polyhedron. Here F stands for faces, V for vertices and E for the edges of the polyhedron.

**Convex**

**polyhedron**

In a convex polyhedron, the line segment joining any two points on the surface of the polyhedron lies entirely inside or on the polyhedron.

**Concave polyhedron**

A polyhedron some of whose plane sections are concave polygons is known as a concave polyhedron. Concave polygons have at least one interior angle greater than 180° and has some of its sides bent inward.

**Prism**

A prism is a polyhedron with parallel congruent polygon bases and sides made of parallelograms.

**Pyramids**

A pyramid is a polyhedron whose base is a polygon of any number of sides and whose lateral faces are triangles with a common vertex.

Prisms and pyramids are named after the shape of their base.

Maps represent the location of a place or object in relation to other places or objects.