My friends Dave and Patricia have two kids, Xavier and Declan. They're what are technically known as "beautiful" boys: huge eyes, long lashes, button noses, and mischievous grins. Both are sociable and cuddly, but while six-year-old Xavier speaks like an adult, two-year-old Declan doesn't talk yet.
In fact, until a month ago Declan had not even begun to babble or imitate the outside world. He laughed, cried, and screamed with gusto, but the critical aspect of language development was missing. Fortunately, Patricia is trained to help kids with special needs, and she and Dave have been able to get Declan the help that he needed.
Chances are if your child is developmentally delayed, you and your pediatrician will pick up on milestones that just aren't being met.