 Consider again the basic multi-agent epistemic logic with language \(\cL_{\left\{ \oK{1}, \ldots, \oK{n} \right\}}\). As mentioned above, this setting is multi-modal, as its language contains, for each agent \(i \in \ttA\), a knowledge modality \(K_i\) that is semantically interpreted in the standard way with respect to a matching epistemic relation \(R_i\). While a modality for the concept of everybody knows (E) is syntactically definable (provided the set of agents is finite), other group epistemic notions, such as distributed knowledge and common knowledge are  not.[4]