A child of 2 years and 6 months born by Caeserean section well developed and growing well. He has not developed speach fully. He says words like pappa mamma nana, he is vey sharp in other things like playing, wearing shoes etc. He is able to communicate by action and is a very happy and willing to learn games etc.

What is the cause of the delayed speach? Hearing is normal and he obeys orders well. Kindly guide.