Spoken language, then, is composed of a great variety of sounds made with the vocal organs. A word may consist of one sound (as Ah! or O or I), but most words consist of two or more different sounds (as go, see, try, finish). Long or short, however, a word is merely a sign made to express thought. Thought may be imperfectly expressed by signs made with the head, the hands, etc. Thus, if I grasp a person's arm and point to a dog, he may understand me to ask, "Do you see that dog?" And his nod in reply may stand for "Yes, I see him." But any dialogue carried on in this way must be both fragmentary and uncertain. To express our thoughts fully, freely, and accurately, we must use words, -that is, signs made with the voice. Such voice-signs have had meanings associated with them by custom or tradition, so that their sense is at once understood by all. Their advantage is twofold: they are far more numerous and varied than other signs; and the meanings attached to them are much more definite than those of nods and gestures. Written words are signs made with the pen to represent and recall to the mind the spoken words (or voice-signs). Written language (that is, composition) must, of necessity, be somewhat fuller than spoken language, as well as more formal and exact..