What is Yield to maturity?
The annual return on a bond held to maturity, counting both the coupons and the difference between what you paid and what you are repaid.
It is solved rather than calculated directly, because there is no algebraic way to isolate it. It assumes every coupon is reinvested at the same yield, which is rarely what happens.
Not to be confused with Current yield
Current yield is the annual coupon divided by the price and stops there. On a bond bought below face it understates the return, because it ignores the gain collected when the bond redeems at face.