A perpetuity is an asset or a contract that pays a fixed amount of money each time period, forever.

永续年金是一种财产或者合同,规定在每一时间段内,支付一定数量的货币,直至永远

耶鲁公开课 - 金融市场课程节选

Suppose someone has a contract that promises to pay an amount each period over a number of years.

假设某人有一份合约,承诺在数年内的不同时段内分开支付

耶鲁公开课 - 金融市场课程节选