+258.+ From our study of the adjective, we know that it is a word used
with a noun to qualify or limit its meaning. But a great many times we
find these adjectives used without the noun which they modify. As, for
example, I may say, _This is mine_, and the adjective _this_ is used
alone without the noun which it modifies, and you are able to tell only
by what I have been saying or by some action of mine to what I am
referring when I say _this_.
When adjectives are used in this manner, they are used like pronouns--in
place of a noun. So sometimes we find an adjective used with a noun, and
sometimes used as a pronoun, in place of a noun; and since we name our
parts of speech by the work which they do in the sentence, an adjective
used in this way is not an adjective, but a pronoun or word used in
place of a noun.
So these words are pronouns when they stand alone to represent
things--when they are used in place of a noun. They are adjectives when
they are used _with_ a noun to limit or qualify the noun. For example, I
may say, _This tree is an elm, but that tree is an oak_. _This_ and
_that_ in this sentence are adjectives used to modify the noun _tree_.
But I may say, _This is an oak and that is an elm_, and in this sentence
_this_ and _that_ are used without a noun, they are used as pronouns.
+259.+ Our being able to name every part of speech is not nearly so
important as our being able to understand the functions of the different
parts of speech and being able to use them correctly. But still it is
well for us to be able to take a sentence and point out its different
parts and tell what each part is and the function which it serves in the
sentence. So sometimes in doing this we may find it difficult to tell
whether certain words are adjectives or pronouns. We can distinguish
between adjectives and pronouns by this rule:
When you cannot supply the noun which the adjective modifies, from the
_same_ sentence, then the word which takes the place of the noun is a
pronoun, but if you can supply the omitted noun from the same sentence,
then the word is used as an adjective. Thus, we do not say that the noun
is understood unless it has already been used in the same sentence and
is omitted to avoid repetition. We make each sentence a law unto itself
and classify each word in the sentence according to what it does in its
own sentence.
So if a noun does not occur in the same sentence with the word about
which we are in doubt as to whether it is a pronoun or adjective, it is
a pronoun or word used in place of a noun. For example, in the sentence,
_This book is good but that is better_; _book_ is understood after the
word _that_ and left out to avoid tiresome repetition of the word
_book_. Therefore _that_ is an adjective in this sentence. But if I say,
_This is good, but that is better_; there is no noun understood, for
there is no noun in the sentence which we can supply with _this_ and
_that_. Therefore in this sentence _this_ and _that_ are pronouns, used
in place of the noun. And since _this_ and _that_, when used as
adjectives, are called demonstrative adjectives; therefore when _this_
and _that_, _these_ and _those_, and similar words, are used as pronouns
they are called demonstrative pronouns.
+260.+ Be careful not to confuse the possessive pronouns with
adjectives. Possessive pronouns modify the nouns with which they are
used, but they are not adjectives, they are possessive pronouns. _My_,
_his_, _her_, _its_, _our_, _your_ and _their_ are all possessive
pronouns, not adjectives. Also be careful not to confuse nouns in the
possessive form with adjectives.