My niece have a little boy who is turning 2 old Sept 8th.  She has been concerned for some time about the lack of words.  I never noticed until she pointed it out to me.  I get the impression that she is thinking Autism, but I'm not so sure.  He is very social, and shares more so than my 3 yo DD.  My niece said he is a little terror at times (which I've never witnessed).  He usderstands what is being said to him, and gets his point across, just not using words.  I know there is a wide spectrum of Autism, but I know there are SD & D too.  The dr keeps telling her the he's not talking because he is a second child; and how many of us have been told that before!