| Word | Meaning |
| Light | A form of energy that makes objects visible. |
| Reflection | The returning of light after it falls on an object. |
| Mirror | A device that reflects light and forms a picture of an object. |
| Plane mirror | A mirror whose reflecting surface is flat. |
| Spherical mirror | A mirror whose reflecting surface is curved like a piece of a ball. |
| Concave mirror | A mirror with its middle pressed in and its edges raised. |
| Convex mirror | A mirror with its middle raised and its edges pressed in. |
| Converging mirror | Another name for a concave mirror, because it gathers rays at one point. |
| Diverging mirror | Another name for a convex mirror, because it spreads rays apart. |
| Erect | A picture that stands the same way up as the object. |