My son is just a week shy of 18mths and doesn't talk. He can say mumma and dada when he's agitated and wants us but doesn't talk or anything. Lots of squeals at us and snorts. I wasn't concerned at all. I'm still not. I do believe he will start on his own terms.
So I suggest you follow the advice from the previous posters but also try not to worry too much. Because sometimes you wonder if they are behind and then they wake up one day and never shut up again.