3.  Etymology treats of the derivation of words; that is, it teaches you how one word comes from, or grows out of another.  For example, from the word speak, come the words speak_est_, speak_eth_, speak_s_, speak_ing_, sp_oke_, spo_ken_, speak_er_, speak_er’s_, speak_ers_.  These, you perceive, are all one and the same word, and all, except the last three, express the same kind of action.  They differ from each other only in the termination.  These changes in termination are produced on the word in order to make it correspond with the various persons who speak, the number of persons, or the time of speaking; as, I speak, thou speak_est_, the man speak_eth_, or speak_s_, the men speak, I sp_oke_; The speak_er_ speak_s_ another speak_er’s_ spe_ech_.

The third part of Etymology, which is intimately connected with the second, will be more amply expanded in Lecture XIV, and in the Philosophical notes; but I shall not treat largely of that branch of derivation which consists in tracing words to foreign languages.  This is the province of the lexicographer, rather than of the philologist.  It is not the business of him who writes a practical, English grammar, to trace words to the Saxon, nor to the Celtic, the Greek, the Dutch, the Mexican, nor the Persian; nor is it his province to explain their meaning in Latin, French, or Hebrew, Italian, Mohegan, or Sanscrit; but it is his duty to explain their properties, their powers, their connexions, relations, dependancies, and, bearings, not at the period in which the Danes made an irruption into the island of Great Britain, nor in the year in which Lamech paid his addresses to Adah and Zillah, but at the particular period in which he writes.  His words are already derived, formed, established, and furnished to his hand, and he is bound to take them and explain them as he finds them in his day, without any regard to their ancient construction and application.

CLASSIFICATION.  In arranging the parts of speech, I conceive it to be the legitimate object of the practical grammarian, to consult practical convenience.  The true principle of classification seems to be, not a reference to essential differences in the primitive meaning of words, nor to their original combinations, but to the manner in which they are at present employed.  In the early and rude state of society, mankind are quite limited in their knowledge, and having but few ideas to communicate, a small number of words answers their purpose in the transmission of thought.  This leads them to express their ideas in short, detached sentences, requiring few or none of those connectives, or words of transition, which are afterwards introduced into language by refinement, and which contribute so largely to its perspicuity and elegance.  The argument appears to be conclusive, then, that every language must necessarily have more parts of speech in its refined, than in its barbarous state.