degree also called arity, adicity, in formal languages, a property of predicate and function expressions that determines the number of terms with which the expression is correctly combined to yield a well-formed expression. If an expression combines with a single term to form a wellformed expression, it is of degree one (monadic, singulary). Expressions that combine with two terms are of degree two (dyadic, binary), and so on. Expressions of degree greater than or equal to two are polyadic. The formation rules of a formalized language must effectively specify the degrees of its primitive expressions as part of the effective determination of the class of wellformed formulas. Degree is commonly indicated by an attached superscript consisting of an Arabic numeral. Formalized languages have been studied that contain expressions having variable degree (or variable adicity) and that can thus combine with any finite number of terms. An abstract relation that would be appropriate as extension of a predicate expression is subject to the same terminology, and likewise for function expressions and their associated functions. See also FORMAL LANGUAGE , MATHEMATICAL FUNC — TION , PROPERTY. C.A.A.