$\huge \braket{f, g} $ Generalized [[Binary Operation]] between any two objects (notable example: [[Dot Product]]) that satifies the following rules: $\large \begin{align} \braket{ f_{1}+ f_{2}, g } &= \braket{f, g} + \braket{f_{2}, g} \\ \braket{kf, g} &= k\braket{f, g} \\ \braket{f, g} &= \braket{g, f} \\ \braket{f, f} &\ge 0\\ \end{align} $ - Must be [[Distributive]] - Any [[Scalar]] can be pulled out of the product - Must be [[Commutative]] - The [[Operation]] between two of the same object must be greater or equal to 0. >[!tip] Used in [[Fourier Decomposition]]