Receptive vocabulary, or understanding of words, is developed even before any words are spoken. By 12 months of age approximately 12 words should be understood by your baby. Your baby may speak his first word around his first birthday. This is the average age however, and this milestone can occur anytime between 10 and 15 months. These were the first words of babies fifty years ago and they are the first words of babies today.
Many parents associate their baby's first spoken word with the onset of language development.
However, as we have seen the development of language begins well before this stage. There are many ways parents can enrich their baby's environment with language which may foster the development of language. Suggestions and examples follow this timeline. In this year your baby's receptive vocabulary will increase to as much as 300 words and his spoken language will increase to an average of 200-275 words. Between 18 and 24 months your toddler will begin to speak using two-word sentences.