So he says about 20 words. Mainly one syllable and about ten of those words begin with b. The end of the words are often not sounded out properly eg. Nightnight etc. He knows mama and dada and uses it but won't shout it really or use it much to get attention. He has gone from knowing about 4 words at 18 months to currently 20 now so he is a late talker. Is this normal? Should I be worried. His understanding and following instructions is absolutely fine and he recognises loads of words and commands. He has only really just started copying sounds such as coughs and sneezes etc.