In mathematics, a property synonymous with perpendicularity when applied to functions .
Two elements of an {{link=inner product space">inner product space are orthogonal when their inner product
for vectors, the dot product (see vector operations ); for functions, the definite integral of their product
is zero. A set of orthogonal vectors or functions can serve as the basis of an inner product space, meaning that any element of the space can be formed from a linear combination (see linear transformation ) of the elements of such a set.