What do newborns know about grammar?

Grammar is the glue of language: it allows us to string words together into any sentence we can imagine. When we watch babies as they learn a language, we may notice learning stages. First, babies will practice making sounds, then they will say individual words, and only then string them into multi-word phrases. However, before they do all that, babies already know a lot more about grammar than you would think!

Consider the sentence: The dog is sleeping. A baby will already notice the difference between content words (such as ‘dog’, ‘sleep’) and grammatical words (such as ‘the’ and ‘is’ ), even before they know what dogs and sleep are and before they know how to use ‘the’ and ‘is’ in a sentence. 

To us adults, it may seem impossible to know the difference between content words and grammatical words without knowing the meanings of these words. Yet, there is another difference between the two: prosody (that is, the intonation variations in speech). Grammatical words are often less stressed (i.e. less loud and shorter) than content words. Newborns can hear this difference, and use it to distinguish the two types of words!
When you speak to your baby, they are learning a little bit of everything at once: the sounds, the words, and the grammar! Babies are real language learning experts!