An adjective is a word or phrase that describes or modifies a noun or, less frequently, a pronoun.
Adjectives can add any type of information. An iPhone, for example, can be expensive, new, old, broken, jailbroken, pink, lost or stolen, among other things. All those words are adjectives because they tell us more about the phone.
Types of adjectives:
Descriptive adjectives, such as benevolent, simple, organic and green, supply information about a characteristic of the noun they modify.
Possessive adjectives, such as his, her, my, your, their and our answer the question "Who does it belong to?" as in my iPhone. (These words are a type of possessive pronoun, as well.)
Demonstrative adjectives, such as that, this, these and those, answer the question "Which one is it?" They indicate a particular item, as in this laptop or that tablet.
Interrogative adjectives, such as which, what and whose are the ones used to ask the questions.
Numbers can be adjectives as well, when they are used to quantify something, like four crashes or five reboots.
Indefinite adjectives, such as any, few, many, some and several, give us information about the nouns they modify but are less specific than adjectives that identify a particular attribute.
Articles, such as a, an and the, are also categorized as adjectives.
When an adjective is combined with a subject and a verb, the word grouping is known as an adjective clause. Here's an example: "My iPhone 5s, which is a vibrant shade of pink, is clearly superior to my sister's black Android phone."