Slow talker

You really don’t have anything to worry about at this stage. Early talkers begin to put words together at about 9 months. Late talkers can stay pretty silent until at least 2 years. Children vary enormously in the age at which they begin to do a whole range of things, and this is quite normal.
His current phrase, ‘What’s that?’, shows he’s already able to put two words together, that he’s keen to learn, and he’s realised he can use language to start a conversation, because he is asking you to reply. This is very encouraging. Children hear and remember words before they use them.
It might help, though, to think about how to help build your son’s vocabulary. When you’re with him, are you comfortable to chat away, even if he can’t answer your questions or chip in with his own thoughts?
Children love to play with other people; simply describing what it is you and he are doing helps children to pick up words. So plenty of play, chats and looking at story and picture books together, with less rather than more TV and videos, should move him on in good time.
The book Baby Talk : Strengthen Your Child's Ability to Listen, Understand, and Communicate, by Sally Ward (Ballantine Books 034 5437071) (£10.95 from Amazon), explores how children learn to talk and suggests lots of activities to promote speech.
If your son is still not speaking more freely by his second birthday, or if you think that something difficult has happened within his life that might be holding him back, it may be time to seek advice from a doctor or speech therapist.