2. Duality

Animals which use vocal signals have a stock of certain sounds they can utter, and in extreme cases, some of them, such as birdes do combine sounds, though it takes place quite seldom. But when it comes to humans we can combine these sound units which are called phonemes to create larger units. By doing so we add another layer to the already existing basic sound units to create a more sophisticated type of language. This process of double layering is known as duality.