什麼是yield to maturity

Yield to maturity (YTM) is the yield promised by the bondholder on the assumption that the bond will be held to maturity, that all coupon and principal payments will be made and coupon payments are reinvested at the bond's promised yield at the same rate as invested. It is a measurement of the return of the bonds.
As the purchase price of the debenture always fluctuate but coupon, principal repayment at maturity and maturity of the debenture is fixed, the YTM is calculated by equating the purchase price of the debenture with the sum of present values of the fixed coupons during its life and principal repayment at maturity.

Solve for YTM where
Market Price =
To achieve a return equal to YTM, the bond owner must:

reinvest each coupon received at this rate,
hold the bond until maturity, and
redeem the bond at par.
The concept of current yield is closely related to other bond concepts, including yield to maturity, and coupon yield. The relationship between yield to maturity and coupon rate is as follows:

When a bond sells at a discount, YTM > current yield > coupon yield.
When a bond sells at a premium, coupon yield > current yield > YTM.
When a bond sells at par, YTM = current yield = coupon yield.