An adjective modifies a noun or a pronoun by describing, identifying, or quantifying words. In other words, an adjective modifies a noun or a pronoun, usually by describing it or making its meaning more specific. Adjectives make the meaning of nouns and pronouns more definite by describing them. An adjective usually precedes the noun or the pronoun which it modifies.

In the following examples, the highlighted words are adjectives:

The pink airplane roared over the treetops.
The large dog barked loudly.
The fish was a big one.
The empty building was dark and dank.
Many stores have already begun to display their Christmas products.
A broken mirror sat on the mahogany dresser.
The storage room was filled with large, yellow corn brooms.

There are five types of adjectives: articles, demonstrative adjectives, indefinite adjectives, interrogative adjectives, and possessive adjectives.

Articles

The most frequently used adjectives are a, an, and the; these words are called articles. Articles always precede the noun or pronoun that they modify, although not always immediately. Articles are categorized as definite or indefinite. A and an are called indefinite articles because the noun to which they refer does not reference a specific person, place, thing, or idea (non-specific or non-particular nouns). Alternately, the is called the definite article because the noun to which it refers references a specific person, place, thing, or idea (specific or particular nouns). Please note that articles are seldom used before pronouns. In the sentences below, words functioning as adjectives are highlighted.

A soldier received the medal.
In the sentence above, an indefinite article “a” makes reference to a soldier, but not a specific soldier. A soldier received the award, but not a soldier specifically identified. Indefinite articles imply a general reference..

While I was in the hospital, an hour seemed like a day.
In the sentence above, an indefinite article “an” makes reference to a hour, but not a specific hour.

The soldier received the medal.
In the sentence above, the definite article “the” is used to identify or indicate a specific soldier received the medal. Whereas the indefinite articles a and an imply general reference, the implies a specific reference.

Demonstrative Adjectives

The demonstrative adjectives “this,” “these,” “that,” “those,” and “what” point out or single out the noun or pronoun to which they refer, Demonstrative adjectives are identical to the demonstrative pronouns, but are used as adjectives to modify nouns or noun phrases.

The soldier was awarded that medal.
In the sentence above, the demonstrative adjective “that” points out a specific medal.

This house needs to be painted.
In the sentence above, the demonstrative adjective points out which house. The demonstrative adjective “this” modifies “house” and the noun phrase “this house” is the subject of the sentence.

Even though my husband preferred those clothes, I bought these.
In the sentence above, the demonstrative adjective points out which clothes. In the subordinate clause, “those” modifies “clothes” and the noun phrase “those clothes” is the object of the verb “preferred.” In the independent clause, “these” is the direct object of the verb “bought.”

Please note that the relationship between a demonstrative adjective and a demonstrative pronoun is similar to the relationship between a possessive adjective and a possessive pronoun, or to that between a interrogative adjective and an interrogative pronoun.

Indefinite Adjectives

An indefinite adjective is similar to an indefinite pronoun, except that it modifies a noun, pronoun, or noun phrase. An indefinite adjective does not point out a specific noun or pronoun, as does a demonstrative adjective; instead, these adjectives modify an unspecific noun or pronoun. Some of the more common indefinite adjectives are: “no,” “any,” “many,” “few,” and “several.” Here are some examples:

Many people believe that they are over-taxed.
The indefinite adjective “many” modifies the noun “people” and the noun phrase “many people” is the subject of the sentence.

I will forward you any mail that arrives after you have moved.
In the sentence above, the indefinite adjective “any” modifies the noun “mail” and the noun phrase “any mail” is the direct object of the compound verb “will forward.”

According to a zoo spokesman, there are no condors in captivity. However, over the past few months, many hikers have reported seeing several condors off in the distance.
The sentence above use quite a few indefinite adjectives.

Please wait here; I'll just be a few more minutes.
Here the indefinite pronoun “few” modifies “minutes” without telling you specifically how many minutes.

Interrogative Adjectives

An interrogative adjective is like an interrogative pronoun, except that it modifies a noun or noun phrase rather than standing on its own. Some of the more common interrogative adjectives are “what,” “which,” “whose,” “whosever,” “whichever,” and “whatever.”

Which toy will the child want?
Like other adjectives, “which” can be used to modify a noun or a noun phrase. In the sentence above, “which” modifies “toy” and the noun phrase “which toy” is the subject of the verb “want.”

What movie are you watching?
In the sentence above, “what” modifies “movie” and the noun phrase “what movie” is the direct object of the compound verb “are watching.”

Possessive Adjectives

A possessive adjective is similar or identical to a possessive pronoun; however, it is used as an adjective and modifies a noun or a noun phrase. Some of the more common possessive adjectives are “my,” “your,” “his,” “her,” “its,” “our,” and “their.”

Is that my book on the table?
In the sentence above, the possessive adjective “my” modifies the noun “book.”

What is your phone number?
In the sentence above, the possessive adjective “your” is used to modify the noun phrase “phone number.”

The restaurant sold his favorite type of pot roast.
In the sentence above, the possessive adjective “his” modifies the noun phrase “favorite type of pot roast.”

After many months, she returned to her home.
In the sentence above. the possessive adjective “her” modifies the noun “home” and the noun phrase “her home” is the object of the preposition “to.”