A posynomial, also known as a posinomial in some literature, is a function of the form f = ∑ k = 1 K c k x 1 a 1 k ⋯ x n a n k {\displaystyle f=\sum _{k=1}^{K}c_{k}x_{1}^{a_{1k}}\cdots x_{n}^{a_{nk}}} where all the coordinates x i {\displaystyle x_{i}} and coefficients c k {\displaystyle c_{k}} are positive real numbers, and the exponents a i k {\displaystyle a_{ik}} are real numbers. Wikipedia