L2 Inner Product (⟨·,·⟩L2) is a type of inner product (⟨·,·⟩) that takes two real functions 𝑓 and 𝑔 on a measure space (𝑋,𝐴,𝜇) with respect to the measure (𝜇) ⟨f,g⟩L2=∫Xfgd𝜇