1.5 year old children may be able to speak several simple words such as mama, dada, bye-bye, me, and no; however, they will still be doing a lot of babbling most of the time trying to imitate the words that we say. However, not all of this babble is meaningless, often times, if you pay close attention to what your child is babbling and noting the circumstances, you may begin to pick up on what your toddler is trying to tell you or ask you. You may also begin to notice one or two clear words among all the babbles that your toddler says.
While your 18 months old toddler may still have difficulties communicating with you at this age, it should be very clear to you that your child is able to understand a lot of the things you say to him or her. Before we learn to speak, we first learn to understand a language, and this ability to understand what you are saying to your child is their first step towards learning to speak. Don't underestimate your child's ability to comprehend what you are saying. Be patient and pay attention when you talk to them, and you'll quickly notice that they understand a lot of what you are saying to them.
It may be fun to engage in senseless "baby talk" with your toddler, however, it is to your child's benefit that you avoid baby talk, and instead, talk slowly, clearly, using real words and real sentences to communicate. Talking often to your child gives them a lot of exposure and practice to pick up language and speech skills.
Another great way of helping your child's development is to engage in daily reading activities. Have plenty of colorful and interesting children's book around the house, and take a little time each day to read to and read with your toddler. This helps them develop a habit and an enjoyment of reading, and also helps them catch on to the fact that reading is a great way to have fun and engage in imaginative play. Through reading, your child gets even more exposure to expand their vocabulary; learns to distinguish the sounds of words; learns that the squiggles they see represent the sounds in our speech; and also helps stimulate intellectual development. We began reading to our children the day the were born, and began to teach them to read before they were 3 years old through a process of helping them develop phonemic awareness. They all learned to read before age 3. By 3 years and 9 months, our daughter was reading at a grade two level (80% percentile), with a reading age of 7 years 6 months. You can learn how we helped our children learn to read here.
One thing to bear in mind is that children develop at different speeds, and there's a wide spectrum for a 18 months old's language and speech abilities. Some children may only be able to say one or two words, while other children may already be able to speak a dozen or so words.
At 18 months old, a toddler should have developed good habits and a daily routine, and begin to know what certain events will take place during the day. For example, breakfast, lunch, dinner, nap time, book reading time, play time, etc... That is, only if the parents have taken an effort to instill some regularity and routine into the life of the young child. It is best to have a regular routine each day so that your child knows what to expect - after all, we're all creatures of habit.
Intellectual development at one and a half years old includes the continued development and improvement of memory. Your child may remember a toy they were playing with earlier that they had forgotten about, or continue with a task they stopped earlier that they had forgotten about. As your child's language and speech develop during this time, so does his or her understanding of speech. You'll notice that the child understands most instructions you give such as: come get your milk; go wash your hands; please clean up your toys; get your shoes and let's go play outside, and so on...
Learning by imitating continues to play a key role in a small child's learning experiences. They copy what you do, and try to imitate what you say. A lot of the learning by imitating also come from outside sources such as television and other children. If you swear, don't be surprised to hear a swear coming from your child. So, be very careful about what you say and do around your children.