 Some logics employ primitive n-place function symbols—symbols that combine with \(n\) singular terms to form a complex singular term. Thus, for example, the plus sign ‘+’ is a two-place function symbol that, when placed between, say, ‘2’ and ‘3’, forms a complex singular term, ‘\(2 + 3\)’ that denotes the number five. Similarly, ‘\(^2\)’ is a one-place function symbol that, when placed after a term denoting a number, forms a complex singular term that denotes that number’s square. Semantically, the extension of a function symbol is a function whose arguments are members of the quantificational domain \(\bD\), and the resulting complex term denotes the result of applying that function to the referents of the \(n\) component singular terms, taken in the order listed. Since classical logic requires every singular term (including those formed by function symbols) to refer to an object in \(\bD\), for each such function symbol \(f\), it requires that: