Babies listen to people talking from the time they are born, and so they are learning language from the very beginning. Adults tend to use exaggerated 'baby-talk', stressing particular parts of speech and attracting the baby's attention. From the age of six months babies begin to concentrate on their own language. They stop babbling by nine months or so and later learn single words, two-word speech, and whole sentences around the age of three. By the age of 18, you may have learnt around 60,000 different words.