Since poetry is an art of speech, we can understand it only through a study of words, which are its media. A single word is seldom an integral element of speech; yet it may fairly be called the atom, the ultimate constituent of speech. Now a word is a structure of a potentially fourfold complexity. First, it is a phenomenon of sound and movement--something heard and uttered. Its sound, and the movement-sensations from vocal cords and tongue and lips which accompany its production, are the sensuous shell of the word. Second, embodied in this as the speaker utters it, associated to it as the hearer understands it, is its meaning. The meaning is either an idea of a concrete thing or situation, or an abstraction. This is the irreducible minimum of a word, but is seldom all. For, in poetry, some emotional response to the object meant by the word impels to its utterance, and this is embodied in it when it is uttered, and a similar feeling is awakened in the auditor when it is heard or read. A word not only mirrors a situation through its meaning, but preserves something of the mind's response; it communicates the total experience,--the self as well as the object. Finally, the meaning of a word may not remain a mere idea, but may grow out into one or more of the concrete images of which it is the residuum. When, for example, I utter the word "ocean," I may not only know what I mean and re-experience my joy in the sea, but my meaning may be clothed in images of the sight and touch and odor of the sea--vicariously, through these images, all my sense experiences of the sea may be present in the mind. A word, therefore, sounds and is articulated, means, expresses feeling, and evokes images. All understanding of poetry depends upon the knowledge and proper evaluation of the functioning of these aspects of a word. Let us consider in a general way each one of them.