+17.  The Individual Elements+ of which every sentence is composed are words.  Every word is the sign of some idea.  Each of the words horse, he, blue, speaks, merrily, at, and because, has a certain naming value, more or less definite, for the mind of the reader.  Of these, horse, blue, he, merrily, have a fairly vivid descriptive power.  In the case of at and because, the main office is, evidently, to express a relation between other ideas:  ["I am at my post"], ["I go because I must"].  The word speaks is less clearly a relational word; at first thought it would seem to have only the office of picturing an activity.  That it also fills the office of a connective will be evident if we compare the following sentences:  He speaks in public.  He is a public speaker.  It is evident that speaks contains in itself the naming value represented in the word speaker, but also has the connecting office fulfilled in the second sentence by is.

All words have, therefore, a naming office, and some have in addition a connecting or relational office.

PARTS OF SPEECH

+18.  Parts of Speech.+—­When we examine the different words in sentences we find that, in spite of these fundamentally similar qualities, the words are serving different purposes.  This difference in purpose or use serves as the basis for dividing words into eight classes, called Parts of Speech.  Use alone determines to which class a word in any given sentence shall belong.  Not only are single words so classified, but any part of speech may be represented by a group of words.  Such a group is either a phrase or a clause.

A phrase is a group of words, containing neither subject nor predicate, that is used as a single part of speech.

A clause is a group of words, containing both subject and predicate, that is used as part of a sentence.  If used as a single part of speech, it is called a subordinate, or dependent, clause.  Some grammarians use the word clause for a subordinate statement only.

+19.  Classification.+—­The eight parts of speech may be classified as follows:—­

  I. Substantives:  nouns, pronouns. 
 II.  Assertives:  verbs. 
III.  Modifiers:  adjectives, adverbs. 
 IV.  Connectives:  prepositions, conjunctions. 
  V. Interjections.

+20.  Definitions.+—­The parts of speech may be defined as follows:—­

(1) A noun is a word used as a name.

(2) A pronoun is a word used in place of a noun, designating a person, place, or thing without naming it.

(3) An adjective is a word that modifies a substantive.

(4) A verb is a word that asserts something—­action, state, or being—–­ concerning a substantive.