add-on

[ad-on, -awn] /ˈædˌɒn, -ˌɔn/
noun
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.
adjective
5.
being installed or provided as an add-on:
an add-on speaker system.
Origin
1945-50; noun and adj. use of verb phrase add on
Examples from the web for add-on
  • None of the add-on image programs zoom as well, they all stop at the pixel block level.
  • The first order of business is to figure out if there is some add-on to the hypothesis that can explain this water.
  • But because it is sold as an add-on, other channels are in effect increasing its price.
  • The mortgage rates do not include add-on fees known as points.
  • The rates do not include add-on fees, known as points.
  • In addition to formal sit-down meals, several restaurants will have special treats, desserts or add-on options for the holiday.
British Dictionary definitions for add-on

add-on

noun
1.
a feature that can be added to a standard model or package to give increased benefits
Word Origin and History for add-on
n.

"additional component," 1941, from add (v.) + on.