The supremum is the least upper bound of a set S, defined as a quantity M such that no member of the set exceeds M, but if ϵ is any positive quantity, however small, there is a member that exceeds M - ϵ. When it exists (which is not required by this definition, e.g., sup R does not exist), it is denoted sup_(x element S) x (or sometimes simply sup_S for short). The supremum is implemented in the Wolfram Language as MaxValue[f, constr, vars].