Etymology

Today it means: A function of the form f(x_1,x_2,…,x_n)=∑ₖ₌₁ᴷc_kx_1^(a_1k)⋯x_n^(a_nk), where all the coordinates x_i and coefficients c_k are positive real numbers, and the exponents a_ik are real numbers. Full definition →