The 2nd person pronouns of a language express a two-way politeness distinction towards addressees, either familiar or honorific.  In French, a speaker may use <i>tu</i> 'you.SG.FAM' for a casual address or <i>vous</i> 'you.HON' for more formal situations.  

<br><br><b>Reference</b><br>
Helmbrecht, Johannes. 2008. Politeness Distinctions in Pronouns.
In Haspelmath et al (2008), chapter 45. Available online at <a href="http://wals.info/feature/45">
http://wals.info/feature/45</a href>.
