The return on an investment is how much you made from the investment as a percent of the money invested.

投资的收益是指,你在整个投资中赚的钱占本金的百分比

耶鲁公开课 - 金融市场课程节选

Now, underlying our theory is the idea that we measure the outcome of your investment in your portfolio by the mean of the return on the portfolio and the variance of the return on the portfolio.

而理论的基础是,我们通过计算,组合收益率的均值，和组合收益率的方差,来衡量一个投资组合的优劣。

耶鲁公开课 - 金融市场课程节选

Suppose someone has been investing money for n years and xi is the return on the investment in a given year.

假设有人投资了n年,Xi是第i年的收益率

耶鲁公开课 - 金融市场课程节选