There appears to be a ‘window’ of learning language that ‘opens’ at about the age of ten months. Infants can hear much earlier, of course, and there is some evidence that they can even hear in the womb. It is clear that they will begin to imitate the ‘noises’ they hear, and when there is a reaction from those surrounding them. They begin to associate meanings with the sounds. Over the next two years, infants acquire language at an astonishing rate. By the age of three, they have acquired basic syntax (sentence structure), basic grammar (the ‘rules’ of the language), and a large vocabulary of basic words necessary to their physical and emotional survival. Their motivation to communicate and talk is high: asking for something usually results in being given the thing they need. Similarly, when the infant begins to play outside, with other children, then the motivation to talk to these children is high, and the infant will try to learn the language of play.
THE IMPORTANT THING TO REMEMBER IS THAT EACH CHILD IS AN INDIVIDUAL, and that each child will learn when they are ready to learn. If you think your child is ‘late’ learning to talk, be sure you have ruled out all possible physical causes and then just wait. Especially if there is more than one language in the baby’s home environment, then the baby will be learning first to process and separate the different languages, before talking begins. This ‘separating the languages process’ is why it is important that each parent speaks only their mother-tongue to the baby. They can speak a third language among themselves if they want the baby to hear and become familiar with that language as well, but it is important that the baby hears native-speaker sounds if you want the baby to make native-speaker sounds.
In the Western world, there are speech therapists and medical doctors who advise parents of young children growing up with more than one language to stop using one of those languages with their children. The language usually told to be stopped being used is the ‘weaker’ language, the one not being used in the overall environment. E.g. in England any other language apart from English may be advised to be stopped altogether.
The top reason for this is because according to some, hearing 2+ languages confuse a child, and result in dire difficulties in learning language at all. The other top reason is that apparently learning the ‘main’ language of where one lives is easier without competition from learning a second language.
However, to date there is NO evidence, scientific or other, that hearing two or more languages leads to delays or disorders in language attainment. Countless children world wide learn more than one language from birth and don’t show any of the ‘side effects’ which apparently come with learning 2+ languages. This is visible proof that there is no causal relationship between learning more than one language and language learning problems.