In a linear programming problem involving a set of variables x_j , j = 1, 2, ..., n, a function of the form c₁x₁ + c₂x₂ + . . . + c_nx_n (where the c_j are constants) which one wishes to optimize (maximize or minimize, depending on the problem) subject to a set of restrictions.

Any function from a vector space into its scalar field.