First Sentence

"An optimization problem is the task of minimizing (or maximizing - for definiteness we discuss minimization) a certain real-valued "objective functional" (or "cost", or "energy", or "performance index", etc.) E( ), possibly under a set of equality and/or inequality constraints, where = ( 1,..., n) is a vector (often the discretization of one or several functions) of unknown variables (real or complex numbers, and/or integers, and/or Ising spins, etc.)."