Crying is one of a baby's first ways of communicating through sound.

By the time a baby is four weeks old, she will cry in different ways for different things. There is a unique cry for hunger, wetness, pain and missing company or contact. Within a few months, babies also start to coo and gurgle with pleasure.

Within 3-4 months, babies realise that when they make noise, people respond. When a parent or caregiver responds to a baby's cries, the baby begins to trust her means of communication, because her needs are being met. In the second six months of life, babies begin to babble in the language of their parents and other caregivers.

Babies and toddlers do not understand words out of context. Instead, they understand words in combination with your gestures, tone and facial expression.

By 18-24 months, toddlers begin to use action words. These words express what they see or want, leaving out adjectives and other grammatical conventions. They may come out with short phrases such as ‘Mummy go’, or ‘Shoes on’. Babies and toddlers also speak through gestures and tone of voice. What they do physically may be as important as what they actually say.

Toddlers use words and short sentences to assert themselves. ‘No’ and ‘mine’ are used to claim space and take control of their new world. It is developmentally important for a toddler to say these words. When young children say ‘no’ to parents, they are often saying ‘yes’ to themselves. Asserting their independence is an early, important step towards becoming their own person, separate from you.