What is variance of return for a portfolio？

The variance of return for a portfolio is a measure of the variability of the portfolio's returns from its expected value. It is calculated by taking the sum of the squared deviations of each return from the portfolio's expected return, weighted by the proportion of each asset in the portfolio. A higher variance indicates that the portfolio's returns are more spread out and therefore more risky, while a lower variance indicates that the portfolio's returns are more stable and less risky.