Duration is defined as:

Duration is a crucial concept in bond investment and fixed income analysis, as it measures the sensitivity of a bond's price to changes in interest rates. Specifically, it reflects the weighted average time until a bond's cash flows are received, indicating how much the price of a bond is expected to change as interest rates fluctuate.

The correct choice emphasizes that duration is indeed a measure of volatility, which is influenced by the coupon rate and yield to maturity. Bonds with lower coupon rates typically have greater duration, meaning they are more sensitive to interest rate changes. Conversely, bonds with higher coupon rates tend to have lower duration, indicating less price sensitivity. Additionally, the yield to maturity plays a vital role in determining the bond's price volatility; as the yield rises, the present value of the bond's future cash flows decreases, thus affecting its duration.

This connection to volatility is critical for investors who want to manage risk in their bond portfolios effectively. Understanding duration helps them gauge how their bond investments might react in different interest rate environments, allowing for more informed decision-making regarding asset allocation and risk management.