Full Idea
In S4 there are fourteen modalities: no-operator; necessarily; possibly; necessarily-possibly; possibly-necessarily; necessarily-possibly-necessarily; and possibly-necessarily-possibly (each with its negation).
Clarification
S4 is one of the five main systems of modal logic
Gist of Idea
There are seven modalities in S4, each with its negation
Source
Rod Girle (Modal Logics and Philosophy [2000], 3.5)
Book Reference
Girle,Rod: 'Modal Logics and Philosophy' [Acumen 2000], p.46
A Reaction
This is said to be 'more complex' than S5, but also 'weaker'.