If you want to know whether a pronoun is an interrogative pronoun, just ask. No, really! An interrogative pronoun is used when asking questions. The trick is, they can actually be only used in a question. Even if they can be used as different kinds of pronouns in different contexts, you can only call them interrogative pronouns if they are being used in a question format.
An interrogative pronoun often stands for something that we are not aware of yet, because we are asking about it. We use these pronouns specifically to ask questions. These pronouns are special because they all start with "Wh", which makes them easy to remember.
Do not confuse them with what most elementary school teachers call the "5 W's - who, what, where, why, and when," because in reality, these are not all interrogative pronouns.
The interrogative pronouns that most English speakers are aware of are:
whom, whose, who, what, and which
These are the pronouns that help English speakers find out information. The words "whatsoever" and "whichever" are also used sometimes, and they are considered interrogative pronouns as well.
Wait - not so fast! These pronouns can also be used in sentences that are not questions. In those cases, these pronouns are not interrogative.
There are several other words that start with a W - but watch out! They are not interrogative pronouns just because they are words that start with W and are in questions!
Also remember that unlike other pronouns, sometimes interrogative pronouns do not have antecedents because you are not yet sure what they really are!
Below are a few examples of interrogative pronouns being used correctly in questions:
These are a few examples that are incorrect:
In the following short paragraph, see if you can identify all of the interrogative pronouns. Check with your teacher to see if you have selected the right words as interrogative pronouns.
Today, I was getting ready to go to the movie theatre. I thought to myself, "What is playing at the movies this afternoon?" What I wanted to see was a comedy, and I was glad to see that the movie which was playing was one of my favorites. When was the movie? Three o'clock. What time did I get there? I actually arrived a half hour late, which I was not very happy about. Who did I go with? My sister - who was running a bit late. Whatever!
In reality, only a very few interrogative pronouns were used in the above example. It may have looked like more were used, but be careful: just because it starts with a W does not mean it is an interrogative pronoun! Make sure that it was used in a question - and also make sure that it is one of the seven "W question words" that actually function as interrogative pronouns. This exercise was designed to trip you up!
For more exercises, speak with your English teacher or look through a grammar book, and see if your understanding of what an interrogative pronoun is improves over time.