退出(tuì chū) - to withdraw, to quit, to leave, to log out in Mandarin

退出 (tuì chū) is leaving something you had joined: a competition, a party, a treaty, a group chat, an app. Its opposite is 加入 or 参加, and the pair works cleanly, so 加入这个群 and 退出这个群 are the two ends of the same story.

It is not the word for walking out of a room. That is 出去 or 离开. 退出 needs a membership, a contest or a running programme to step out of, something with an inside you had signed up to. The nearest English is "withdraw from" rather than "exit".

The computing sense is worth knowing on day one, because it is on every Chinese phone: 退出 is the button for quitting an app and 退出登录 is logging out. 退 on its own also carries the money sense of giving something back, as in 退货 (return goods) and 退票 (refund a ticket), so the character is well worth the effort.