§ =6.= Before going further it will be well to define exactly the meaning of the word _accent_, and to give an account of its different uses. Accent is generally defined as 'the stronger emphasis put on a syllable, the stress laid on it', or, as Sweet[4] puts it, 'the comparative force with which the separate syllables of a sound-group are pronounced.' According to Brücke[5] it is produced by increasing the pressure of the breath. The stronger the pressure with which the air passes from the lungs through the glottis, the louder will be the tone of voice, the louder will be the sound of the consonants which the stream of air produces in the cavity of the mouth. This increase of tone and sound is what is called 'accent'. Brücke seems to use tone and sound as almost synonymous, but in metric we must distinguish between them. Sound (_sonus_) is the more general, tone ([Greek: tonos]) the more specific expression. Sound, in this general sense, may have a stronger or weaker tone. This strengthening of the tone is usually, not invariably, accompanied by a rise in the pitch of the voice, just as the weakening of the tone is accompanied by a lowering of the pitch. In the Teutonic languages these variations of stress or accent serve to bring into prominence the relative importance logically of the various syllables of which words are composed. As an almost invariable rule, the accent falls in these languages on the root-syllable, which determines the sense of the word, and not on the formative elements which modify that sense. This accent is an expiratory or stress accent.
It must be noted that we cannot, using the term in this sense, speak of the accent of a monosyllabic word when isolated, but only of its sound; nor can we use the word _accent_ with reference to two or more syllables in juxtaposition, when they are all uttered with precisely the same force of voice. The term is significant only in relation to a _variation_ in the audible stress with which the different syllables of a word or a sentence are spoken. This variation of stress affects monosyllables only in connected speech, where they receive an accentuation relative to the other words of the sentence. An absolute uniformity of stress in a sentence is unnatural, though the amount of variation in stress differs greatly in different languages. 'The distinctions of stress in some languages are less marked than in others. Thus in French the syllables are all pronounced with a nearly uniform stress, the strong syllables rising only a little above the general level, its occurrence being also uncertain and fluctuating. This makes Frenchmen unable without systematic training to master the accentuation of foreign languages.'[6] English and the other Teutonic languages, on the other hand, show a marked tendency to alternate weak and strong stress.