In most systems the formators, or “logical” signs, are given by enumeration. - Weinreich (1963), a pag.120
Languages contain signs of two kinds: every sign is, in general, a designator or a formator [...]; a formator consists of a sign-vehicle and an implicit instruction for an operation, such as negation, generalization, and the like [...]. - Weinreich (1963), a pag.116