title: Why does is.vector() return TRUE for list?
body: <p>I'm an R beginner.  Browsing the R documentation, I stumbled upon this sentence <code>?is.vector</code>: 
  <em>"If mode = "any", is.vector may return TRUE for the atomic modes, list and expression."</em></p>
  
  <p>I'm just curious - why?  All of the documentation I've read states that lists and vectors are two different data types.  Is there some deeper R datatype concept I'm not getting?</p>