[ad-on, -awn] 
| 1. | a device or unit added to equipment or a construction: an add-on to a computer; a nice add-on to an old house. |
| 2. | an extra charge: Add-ons for taxes and tour guide fees boosted the price of the vacation to $2,500. |
| 3. | an additional item, as a rider or provision: This is just another legislative add-on. |
| 4. | anything added on: a hi-fi system that can be augmented with add-ons like extra speakers. |
| 5. | being installed or provided as an add-on: an add-on speaker system. |
add-on