According to a time-honored tradition in finance, it says that it's a promise to pay $1, but it's not worth $1 today.

由于资金有时间价值,他说他承诺支付一美元,但在此时此刻它并不值一美元

耶鲁公开课 - 金融市场课程节选

What really matters to you as an investor is how much you have to pay today to get $100 in sixty days.

对于一个投资者来说,重要的是,现在你需要支付多少钱,才能在60天后获得100美元

耶鲁公开课 - 金融市场课程节选

For example, I may have someone who promises to pay me $1 in one year or in two years or three years.

举个例子,有人对我承诺,在一年或者两年或者三年内支付我一美元

耶鲁公开课 - 金融市场课程节选

Of course, there would be larger denominations than $100, but by tradition, we speak of them as if they were bonds that you paid $100 to get.

当然,面额肯定大于100美元,但是按照传统,我们在讨论长期债券的时候,就假设你支付了100美元

耶鲁公开课 - 金融市场课程节选

Generally, if it pays c dollars for every period, the present value is c/r.

推广开来,如果在每段时期内支付c美元,那么它的现值就是c/r

耶鲁公开课 - 金融市场课程节选