Orthonormal function system

An orthonormal function system (ONS) is an orthonormal basis in a vector space of functions.[1]This linear algebra-related article is a stub.You can help Wikipedia by expanding it.This mathematical analysis–related article is a stub.You can help Wikipedia by expanding it.
orthonormalvector spacefunctionsbasis (linear algebra)Fourier analysissquare-integrableHilbert spacelinear algebramathematical analysis