Many parents believe that by 18 months a child should be speaking a lot. But in fact, an article found under Baby Center and toddler language development, states that toddlers at the age of 18 months, toddlers speak about 5 words. However, they understand near 50 words.
If you were a parent who chose to teach baby sign language, then your toddler could be communicating up to 50 words at this age. That is a 6 month head start on most children, as most toddlers begin speaking 50 words at around the age of 2.
I know with my own son, he was communicating approx 50 words by 18 months. It made our relationship stronger and he didn't have any meltdowns or frustrations due to lack of understanding and communication.
Something to think on.