Interrogative Adjectives 

What is an interrogative adjective?

Like all adjectives, interrogative adjectives (also known as interrogative determiners) modify nouns and pronouns. English has three interrogative adjectives: what, which, and whose. They are called “interrogative” because they are usually used to ask questions. For example:

“What book are you reading?

“Which shirt are you going to buy?”

“Whose computer is this?”

In each of the examples, the interrogative adjective modifies the noun it immediately precedes: book, shirt, and computer.

How to Use Interrogative Adjectives

The interrogative adjectives what and which can often be used interchangeably, while whose is very different. Let’s look at when to use each:

What vs. Which

Although what and which are often interchangeable, there is a subtle difference between the two.

Generally, we use what when the amount of possible answers is unknown or unlimited, and we use which when we either know how many choices there are, or we consider the options to be more limited. Think about the difference between these two sentences:

“What present do you think you’ll get for Christmas?”

“Which present do you think you’ll get for Christmas?”

In the first sentence, the speaker does not have any idea how many possible presents there are. In the second sentence, it seems that the speaker does have an idea of what the presents may be, and that the choices are limited.

Let’s look at a similar example:

“What movie do you want to see?”

“Which movie do you want to see?”

Again, in the first sentence, it seems like the options are unlimited, while in the second sentence, the speaker may have been discussing two or three movies with the listener, and they are trying to make a final decision.

In most instances, we can use either what or which without causing confusion for the reader. However, if there is clearly a limited number of options to choose from, which is the preferred interrogative adjective to use.

Whose

Whose is an adjective that denotes possession, or belonging. We can use it to ask who the owner of an object is. For example:

“Whose socks are on the floor?”

“Whose book is this?”

“Whose turn is it?”

In these examples, the speaker is trying to find out who the socks, book, and turn belong to.

Direct questions

When interrogative adjectives appear in normal direct questions, they are placed at the beginning of the sentence and are immediately followed by the noun that they modify. All the examples that we have seen up until this point were direct questions. However, interrogative adjectives don’t only appear in direct questions.

Indirect questions

Interrogative adjectives can also appear within indirect questions. When this happens, they appear in the middle of the sentence, but they still immediately precede the modified noun. Some indirect questions are used to express politeness:

“Could you tell me whose socks are on the floor?”

“Would you mind telling me which way is north?”

“Do you know what day it is?”

Other indirect questions are used to ask for clarifying information, or to convey surprise:

“You want which computer for Christmas?”

“You’re going out with whose brother?”

“He wants to watch what movie?”

In such cases, emphasis is put on the interrogative adjective—we can hear the stress on the words when we say the sentences aloud.

In reported questions

Interrogative adjectives also appear in the middle of reported questions. Reported questions are also indirect; they tell us about questions. For example:

“She wants to know whose socks are on the floor.”

“He asked which way was north.”

“I asked you what day it was.”

The speaker in each of the examples isn’t asking a definite question, but rather is reporting or clarifying a question that has already been asked.

Other statements

Interrogative adjectives are sometimes used in other statements that aren’t questions at all: they don’t ask questions, either directly or indirectly, but still modify the nouns in the same kind of way. For example:

“I can’t remember whose socks they are.”

“I don’t know which way is north.”

“I know what day it is.”

Common Mistakes

Interrogative Adjectives vs. Interrogative Pronouns

The most common mistake regarding interrogative adjectives is confusing them with interrogative pronouns. This is because all three interrogative adjectives, what, which, and whose, can also function as interrogative pronouns. An easy way to be sure whether you are dealing with an interrogative adjective or an interrogative pronoun is to check whether the question word is immediately followed by the noun it modifies, like in all the examples that we have seen.

“What book is your favorite?”

In this example, what is immediately followed by the noun book. We can be sure that, in this case, what is an interrogative adjective.

“What are you reading?”

In this sentence, what is not immediately followed by a noun that it modifies, which means that in this case, it is an interrogative pronoun.

Just remember: Even though all interrogative adjectives are question words, not all questions words are interrogative adjectives.

Whose vs. Who’s

Finally, beware of the common error of confusing whose and who’s. Whose is an interrogative adjective or pronoun, while who’s is the contraction of who is.