Toddlers can often have trouble with pronunciation and difficulties putting sentences together, but by age 3, most of what your child says should be pretty understandable. If the problem does not seem to be pronunciation, but rather that your child is not talking or talking very little, you should act more quickly.
Check out this article by Patricia McAleer-Hamaguchi on babycenter.com for more indicators that your toddler may need speech therapy.
https://www.babycenter.com/404_what-are-the-indications-that-my-toddler-needs-a-speech-ther_11627.bc
