add-on

noun

(sometimes attributive) Something which can be appended to something else.

I purchased an add-on for my computer.

意味（1）

(sometimes attributive) Something which can be appended to something else.

Payments made before an add-on sale must be allocated entirely to the previous contract or contracts.

意味（2）

Microdrives that can hold several gigabytes (see Figure 2.20) have been available as add-ons for portable devices.

意味（3）

(poker) Additional chips that can be purchased at specific times in tournament play.