a small square on a paper form where you can put a tick to show that you want something or that something is correct or has been dealt with

A check box on the registration form lets you sign up for the service. 注册表单上的勾选框可让您注册该服务。

a small square on a computer screen that you click on to show a choice, to make the computer perform a particular action, etc.

To prevent a program from starting up, clear the check box next to it and click OK. 要防止一个程序启动，请清空它旁边的复选框，然后点击确定。