inner product

Also called dot product, scalar product. the quantity obtained by multiplying the corresponding coordinates of each of two vectors and adding the products, equal to the product of the magnitudes of the vectors and the cosine of the angle between them.

the integral of the product of two real-valued functions.

the integral of the product of the first of two complex-valued functions and the conjugate of the second.

a complex-valued function of two vectors taken in order, whose domain is a vector space.