Why in the product notation, if the top value is less than the bottom one, the product results to $1$?

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As an example, for any one dimensional real valued function $f$, if $q<k$ then $\prod_{i=k}^q f(i)=1$. I thought it was $0$ and that was breaking my intuition about some formulas I'm working with. This makes much more sense. Why is this true? Has the fact that the zeroth power of any real number equals one has anything to do with this?