Interest-Rate & Reinvestment Risk
Interest-rate risk is the chance that rising rates push existing bond prices down — worst for long maturities and low coupons; reinvestment risk is its mirror: falling rates force coupons and called principal to be reinvested at lower yields.
These two risks trade off against each other: locking in long maturities raises price risk but reduces reinvestment uncertainty, and vice versa. Laddering maturities is the standard compromise.