T., dear, check out Einstein's bio: he didn't speak, if I remember right, 'till he was about 5. There are more genuine minds who do not speak early.
I was a quiet kid, and did not WANT to speak, I saw no reason for it. I was THINKING.
NOW, go from the positive side, do not get frustrated at all,
but if you feel you want to know something from doctors, ask them also.
EVERY KID IS UNIQUE.
Now, if he does not speak it does not mean he does not understand, right?!
So, I'd suggest you talk to him about everything, read him tales, sing to him (this is a great device, btw), think aloud, what do you want to buy in the store: see, if he listens to you attentively. If he does, he most probably understands all what you say. Talking can come either out of a suddent all at once and clear, or gradually, slowly getting accustomed to this 'device'.
DO NOT PANICK, T. !!!!!! This is extremely important, as your mood and emotions create either friendly or unfriendly atmosphoere: you are like that Fairy who creates the environment. THink what is beneficial for you both, and do it; tears and fear and panick and frustration do not help A BIT but take away your energy,t hat's all.SO please do not waste energy, and take it all calmly, enjoy the time together, and do what good you can do, every moment.
Again, if you really worry in your heart, go to the doctor and talk, ask for advice, but NO PANICK, okay?! :)