The aim of linguistics is to go beyond the study of individual languages to determine what the universal properties of language are, and to establish… - David Crystal

The question “Why do we use language?” seems hardly to require an answer. But, as is often the way with linguistic questions, our everyday familiarity with speech and writing can make it difficult to appreciate the complexity of the skills, we have learned. This is particularly so when we try to define the range of functions to which language can be put.

We now know that linguistic change does not operate in such an across-the-board manner. Some speakers introduce the change into their speech before others; some use it more frequently and consistently than others; and some words are affected before others. A more accurate view is to think of a change gradually spreading through the words of a language – a view that is known as a lexical diffusion. At first just a few people use a change sporadically in a few words (commonly occurring words are influenced very quickly); then a large number of words are affected, with the sound gradually being used more consistently; then the majority of the words take up the change.

The structural properties of the language are many and complex, but at least they are finite and fairly easy to identify: there are only so many sounds, letters, and grammatical constructions, and although there is a huge vocabulary, at least the units are determinate and manageable.