My almost 4yr old son is still not putting 3-4 words together or speaking in sentences at all.how can I help,and encourage him to do so?

Is he in Day care? I feel some shows help them to learn.

What does his doctor say? Has his hearing been checked? At 4 years old he should be talking in complete sentences and this would be a cause for concern. There could be many reasons ranging from hearing, neurological, developmental, autism, or autism spectrum disorder. Is speech the only area where he is delayed? If you can give some more information that may help others to relate if they've experienced something similar. I would not rely on a message board though -- a doctor would best be able to help your son. Best of luck.