This document discusses concepts of risk and return in investment. It defines return as the basic motivating force and principal reward in investment. There are two types of return - realized return which has been earned, and expected return which is anticipated to be earned in the future. Risk refers to the possibility that the actual return may differ from the expected return. There are two main types of risk - systematic/non-diversifiable risk due to overall market factors, and unsystematic/diversifiable risk that is firm-specific. Required return from an investment is determined by the risk-free rate, expected inflation rate, and risk premium. Various measures like variance and standard deviation are used to quantify investment risk.