It is an axiom of modern linguistics that the form of any given word is much more constant than its meaning. It is true that linguistic communication would break down altogether unless it were accepted that some firm correlation existed between form and meaning. When the teacher uses the word chair all the listening pupils have some idea of what she means, so that the sound of the word is a meaningful linguistic signal to them all, yet the possible variation of the shades of meaning it can evoke is enormous, e.g. not only (to take a random, selection) can it refer to an article of household furniture of various types, shapes, sizes, and materials, but to the presiding over a meeting, a professorial appointment, a physical action, &c. When contrasted with the more or less constant form of the word chair, the variation and complexity of its meaning is staggering, for whereas the form of the word chair is subject to change only within a strictly limited phonetic, morphemic, and syntactical range, the range of variation in its meaning is as extensive as the variation in the situations in respect of which it is used.