Ok I can't find the online link to post the article on here but basically it was saying that at 20 months children should be saying about 50 words and starting to string together short sentences e.g. "where daddy?".
DS is 20 months and really only says the following words:
mummy
daddy
mama (grandma)
car/chair (sound the same!)
He has also said a few other words e.g. stair, hammer, dandan (grandad) but only a couple of times and then seems to have forgotten them.
He makes lots of sounds that aren't really words, like blowing rasberry = helicopter/motorbike noise, coughing = woof, clicking noise = tick-tock (clock) and clip-clop (horse).
He very obviously understands everything you say to him and responds, he just doesn't really speak. He also has lots of non-verbal communications like waving hello/bye bye, pointing, shaking head etc.
Should I be worried?