At a year and a half, most children speak a dozen words (or more) clearly. Besides "Mama" and "Dada," favorite words include "bye-bye," "milk," "cookie," "car," "oh!," and "my." Many 18-month-old toddlers can also link two words together to form rudimentary sentences — sentences without linking verbs or other connecting words. She may say "All gone," "Want ball," or "Me up."
At this stage, it's better to applaud what your toddler can say rather than try to correct "mistakes." For instance, if your child says, "Want cacka," don't correct with, "No, say cracker." Say, "Okay! Here's a cracker!" Modeling the correct use of a word yourself helps kids learn faster than if you correct them outright. And not being constantly corrected will help boost your 18-month-old’s self-confidence and her eagerness to learn and try out new words.