One of the most curious and characteristic features of language, affecting both syntax and style, is idiom. The meaning of the word “idiom” is that which is peculiar, that which is familiar, the word or expression which strikes us or comes home to us, which is more readily understood or more easily remembered. It is a quality which really exists in infinite degrees, which we turn into differences of kind by applying the term only to conspicuous and striking examples of words or phrases which have this quality. It often supersedes the laws of language or the rules of grammar, or rather is to be regarded as another law of language which is natural and necessary. The word or phrase which has been repeated many times over is more intelligible and familiar to us than one which is rare, and our familiarity with it more than compensates for incorrectness or inaccuracy in the use of it. Striking expressions also which have moved the hearts of nations or are the precious stones and jewels of great authors partake of the nature of idioms: they are taken out of the sphere of grammar and are exempt from the proprieties of language. Everyone knows that we often put words together in a manner which would be intolerable if it were not idiomatic. We cannot argue either about the meaning of words or the use of constructions that because they are used in one connection they will be legitimate in another, unless we allow for this principle. We can bear to have words and sentences used in new senses or in a new order or even a little perverted in meaning when we are quite familiar with them. Quotations are as often applied in a sense which the author did not intend as in that which he did. The parody of the words of Shakespeare or of the Bible, which has in it something of the nature of a lie, is far from unpleasing to us. The better known words, even if their meaning be perverted, are more agreeable to us and have a greater power over us. Most of us have experienced a sort of delight and feeling of curiosity when we first came across or when we first used for ourselves a new word or phrase or figure of speech.
There are associations of sound and of sense by which every word is linked to every other. One letter harmonizes with another; every verb or noun derives its meaning, not only from itself, but from the words with which it is associated. Some reflection of them near or distant is embodied in it. In any new use of a word all the existing uses of it have to be considered. Upon these depends the question whether it will bear the proposed extension of meaning or not. According to the famous expression of Luther, “Words are living creatures, having hands and feet.” When they cease to retain this living power of adaptation, when they are only put together like the parts of a piece of furniture, language becomes unpoetical, inexpressive, dead.
Grammars would lead us to suppose that words have a fixed form and sound. Lexicons assign to each word a definite meaning or meanings. They both tend to obscure the fact that the sentence precedes the word and that all language is relative. (1) It is relative to its own context. Its meaning is modified by what has been said before and after in the same or in some other passage: without comparing the context we are not sure whether it is used in the same sense even in two successive sentences. (2) It is relative to facts, to time, place, and occasion: when they are already known to the hearer or reader, they may be presupposed; there is no need to allude to them further. (3) It is relative to the knowledge of the writer and reader or of the speaker and hearer. Except for the sake of order and consecutiveness nothing ought to be expressed which is already commonly or universally known. A word or two may be sufficient to give an intimation to a friend; a long or elaborate speech or composition is required to explain some new idea to a popular audience or to the ordinary reader or to a young pupil. Grammars and dictionaries are not to be despised; for in teaching we need clearness rather than subtlety. But we must not therefore forget that there is also a higher ideal of language in which all is relative—sounds to sounds, words