“pay off”是一个多义的英语短语，核心含义围绕“付出后的结果”，具体用法可分为以下几类，结合含义、词性（及物/不及物）、例句说明：
She worked two jobs to pay off her student loans faster.（她打两份工以便更快还清学生贷款。）
We finally paid off the mortgage on our house last year.（去年我们终于还清了房子的抵押贷款。）
All his late nights studying paid off when he got the top score.（他熬夜学习的努力终于有了回报——他得了最高分。）
Does investing in renewable energy pay off in the long run?（投资可再生能源长期来看有回报吗？）
Her kindness to the new employee paid off when he became her most reliable team member.（她对新员工的善意得到了回报——他成了她最可靠的团队成员。）
The company paid off 50 workers after the project was canceled.（项目取消后，公司解雇了50名员工并付清了工资。）
He was paid off unexpectedly last month, so he’s looking for a new job.（他上个月突然被解雇了，现在在找新工作。）
The shopkeeper paid off the inspector to ignore the safety violations.（店主贿赂检查员，让他忽略安全违规问题。）
They tried to pay off the witness to keep quiet about the accident.（他们试图贿赂证人，让他对事故保持沉默。）
1、 及物 vs. 不及物：
及物（接宾语）：还清债务、解雇、贿赂（如pay off a debt/sb.）；
不及物（不接宾语）：取得成功（如Hard work pays off.）。
2、 常见搭配：
pay off in the long run：长期来看有回报；
pay off a loan/mortgage：还清贷款/抵押贷款；
pay off sb. to do sth.：贿赂某人做某事。
pay back：偿还（欠款）、报复（如I’ll pay you back tomorrow. 我明天还你钱；He paid her back for lying. 他报复了她的谎言）；
pay for：为…付费、为…付出代价（如I’ll pay for dinner. 我来付晚饭钱；You’ll pay for your mistakes. 你会为你的错误付出代价）。
通过以上分类，“pay off”的用法就清晰啦！关键是根据上下文判断具体含义～