Deontic modality refers to possibility related to ability or permission. For example, the sentence <i>You may go home now</i> means that going home is related to permission on the part of the speaker. Epistemic modality, on the other hand, refers to possibility related to available evidence. In the sentence, <i>John must be gone by now</i>, the truth of John’s being gone is evaluated based on available evidence. <br><br>

Both types of modality can be sub-divided into <b>possibility</b> and <b>necessity</b>. An example of <b>Deontic Possibility</b> is the sentence <i>You can go</i>. An example of <b>Deontic Necessity</b> is the sentence <i>You must go</i>. An example of <b>Epistemic Possibility</b> is the sentence <i>He may have left</i>. Finally, an example of <b>Epistemic Necessity</b> is the sentence <i>John must be gone by now</i>. <br><br>

A ‘yes’ value to this property indicates that the same marker is used to indicate both Epistemic and Deontic modality, but only for Possibility Modals. The marker need not have identical syntactic behavior. For example, in Hungarian, the marker <i>lehet</i> indicates either Deontic or Epistemic Modality, but only for Possibility. There is no overlap for Necessity (van der Auwera & Ammann 2008). 

<br><br><b>Reference</b><br>
van der Auwera, Johan & Ammann, Andreas. 2008. Overlap between Situational and Epistemic Modal Marking.
In Haspelmath et al. (2008), chapter 76.
Available online at <a href=â€http://wals.info/feature/76â€>http://wals.info/feature/76</a href>.	

