For the greater dispatch of conversation many words suggest more than one idea; I shall therefore arrange them according to the number and kinds of ideas, which they suggest; and am induced to do this, as a new distribution of the objects of any science may advance the knowledge of it by developing another analogy of its constituent parts. And in thus endeavouring to analyze the theory of language I mean to speak primarily of the English, and occasionally to add what may occur concerning the structure of the Greek and Latin. I. _Conjunctions and Prepositions._ The first class of words consists of those, which suggest but one idea, and suffer no change of termination; which have been termed by grammarians CONJUNCTIONS and PREPOSITIONS; the former of which connect sentences, and the latter words. Both which have been ingeniously explained by Mr. Horne Tooke from their etymology to be abbreviations of other modes of expression. 1. Thus the conjunction _if_ and _an_, are shown by Mr. Tooke to be derived from the imperative mood of the verbs to give and to grant; but both of these conjunctions by long use appear to have become the name of a more abstracted idea, than the words give or grant suggest, as they do not now express any ideas of person, or of number, or of time; all which are generally attendant upon the meaning of a verb; and perhaps all the words of this class are the names of ideas much abstracted, which has caused the difficulty of explaining them. 2. The number of Prepositions is very great in the English language, as they are used before the cases of nouns, and the infinitive mood of verbs, instead of the numerous changes of termination of the nouns and verbs of the Greek and Latin; which gives greater simplicity to our language, and greater facility of acquiring it. The prepositions, as well as the preceding conjunctions, have been well explained by Mr. Horne Tooke; who has developed the etymology of many of them. As the greatest number of the ideas, we receive from external objects, are complex ones, the names of these constitute a great part of language, as the proper names of persons and places; which are complex terms. Now as these complex terms do not always exactly suggest the quantity of combined ideas we mean to express, some of the prepositions are prefixed to them to add or to deduct something, or to limit their general meaning; as a house with a party wall, or a house without a roof. These words are also derived by Mr. Tooke, as abbreviations of the imperative moods of verbs; but which appear now to suggest ideas further abstracted than those generally suggested by verbs, and are all of them properly nouns, or names of ideas. II. _Nouns Substantive._