a system that is used to make sure that a human being, not a machine, is using a computer. The person may be asked to type in a series of letters or numbers, or to complete a simple game. The word captcha is made up of the first letters of words in the phrase Completely Automated Public Turing test to tell Computers and Humans Apart.

The leading ticket sales website is to stop using the human verification system captcha in favour of something more user-friendly. 几家最大的售票网站放弃了人机鉴别验证码系统，转而采用界面更为友好的办法。