pay it forward
主动帮助他人，期望他们将好意传递下去
口语·倡导善意传递
英文释义
to do something kind or helpful for someone without expecting anything in return, with the hope or expectation that they will do something kind or helpful for someone else
例句
A stranger bought my coffee, so I decided to pay it forward by buying lunch for the next person.
典故来源
源自2000年同名电影《Pay It Forward》，但概念更早，强调善行循环传递而非直接回报。