"The problem with interest rates are that you are not modeling a single number, you are modeling a whole term structure, so it is a sort of different type of problem"

This quote by John C. Hull is describing the trouble of forecasting rate of interest. Rates of interest are not just a single number, however rather a term structure that is composed of several numbers. This means that anticipating rates of interest is a lot more complicated issue than anticipating a single number. It requires a much deeper understanding of the financial environment and the aspects that influence interest rates. Moreover, the term structure of rates of interest is constantly changing, making it even more difficult to accurately predict. Therefore, anticipating interest rates is a distinct issue that needs a various approach than predicting a single number.