To figure out if your son is on track, it's important to look at the two aspects of language development. "Receptive vocabulary" refers to the words that a child can understand. It sounds like your son's receptive vocabulary is quite good. He's responding appropriately to your requests and can follow simple directions. "Expressive vocabulary" refers to the words that your child can say and use to communicate. Between ages 2 and 3, a child's expressive vocabulary will typically increase to about 300 words. Children should be saying new words each month and using two-word phrases, such as "more juice."
According to these benchmarks, your son may be behind in his expressive language development. But don't forget to factor in his ability to communicate with gestures. For example, while a child may not say with words "Mommy, I'm hungry. I want a banana," he may take your hand, walk to the kitchen, and point to the banana. If your son is doing this kind of complex gesturing to communicate, he's on the right track and the words will likely come soon.
In any case, I would suggest you consult your son's doctor, who can assess whether there is a medical cause for a speech delay. Also you can call your state's "Child Find" office. They provide assessment services for babies, often at no charge, as well as early-intervention services such as speech therapy. It may very well be that an assessment concludes that your child is doing fine and will catch up on his own, but it's good to check things out, if only for reassurance.
In the meantime, promote your son's language skills by labeling any sounds he uses for words. For example, if he says "ba" for "ball," you should say, "Yes, that's the ball." Continue to talk and sing to him, ask him questions, point out and identify the people and things that fill his world, and read together.
Originally published in American Baby magazine, September 2004. Updated 2009