16 month old not saying words. Adaa.

Hello sir/madam..my son has just turned 16 months old..he is active, playful, loving, social with the people that he knows, however doesnot respond to the people he meets for the first time..he understands many words that we use in daily routine..also follows few instructions..he knows all the people in the close family by names and points towards them when asked...the only issue is that he just doesn't speak meaningful words till now..however he babbles all day like mamama, tatata, nanana, Ataa, adaa...he points towards everything he wants, he also pat us if he wants our attention..speaking meaningful words is the only problem..earlier he had screen time of 1 hour in a day..but now we have reduced it..please help me with this as i am really worried