An inner product of a vector space V over real numbers is a function that associates a real number with every pair of vectors u and v in V in such a way that the following axioms are satisfied for all vectors u, v, and w in V and all scalars k
1. <u,v> = <v,u> (symmetry axiom)
2. <u+v,w> = <u,w> + <v,w> (additive axiom)
3. <ku, v> = k <u, v> (homogeneity axiom)
4. <v,v> >= 0 where <v,v> = 0 if and only if v = 0 (positivity axiom)