 Atomic formulas are defined by means of predicates and terms: If \(R\in \OperSym\) is such that \(\Rank(R)=\langle i_{1},\ldots ,i_{m},0\rangle\), and \(\tau _{1},\ldots \),\(\tau _{m}\) are terms of sorts \(i_{1},\ldots,\) \(i_{m}\), then \(R\tau _{1}\ldots \tau _{m}\) is a formula (when \(R\) is a liberal predicate, we drop the sort requirement for terms). For any terms \(\tau _{1}\ \)and \(\tau _{2}\), the expression \(\tau _{1}\approx \tau _{2}\) is a formula. Notice that the sorts of \(\tau _{1}\ \)and \(\tau _{2}\) do not matter, because our choice of equality symbol is the liberal  one.[3]