The modal operators and are used with their normal meanings in modal logic.

It introduces a temporal model given with modal operators (before, after, etc.).

However, if my next suggestion is very critical, I may continue to use modal operators of possibility.

In order to accommodate notions of common knowledge and distributed knowledge, three other modal operators can be added to the language.

For each modal operator, one needs to transition from a world in the model to a world that is accessible through the accessibility relation.

In doxastic logic, belief is treated as a modal operator.

Most of the other axioms concerning the modal operators are controversial and not widely agreed upon.

The following makes use of the modal operators ("necessarily") and ("possibly").

In (2) t is not within the scope of the modal operator.

As with the modal operator, we will iterate the E function, and .