He's 17 months next week and he doesn't say a single word, not even mama/dada directed at us but he does babble a lot. He doesn't try to copy words either.
I wouldn't be that worried if it wasn't for the fact that his understanding seems to be behind too, there's only a couple of simple directions that he follows which may be he just follows them because he knows the routine (e.g. going to sit on the stairs to wait for me to put his shoes on when I tell him to as that's what we always do when we go outside) but if I ask him things like "give me the ball" or "pick up your hat" he has no clue, just stares blankly at me or wanders off. He does understand when I say it's time to change your nappy or it's time for a nap though as he always laughs and runs away when I say those.
Relevant info - bilingual home, he did fail a hearing check once but then passed a later one, can point to things but doesn't do it much, normal eye contact etc. and sociable (so no concerns about autism), he pretty much just communicates by screaming or grunting at me until I figure out what he wants. I did try to do baby sign language with him but he doesn't get it, doesn't try signs or seem to understand any.