Question words are words that are used in the beginning of a question. Depending on what we are asking about, we need to use different question words.
“When” is used to ask questions about time.
When will she be here? (At what time will she be here?)
When are we leaving? (At what time are we leaving?)
“Who” is used when asking about a person or people. It used for singular and plural questions.
Who is calling me? (What person is calling me?)
Who will give the speech? (What person will give the speech?)
“Whom” is used when asking about the object-person of sentence. It is not frequently used, and in most cases, using “who” suffices.
Whom should I contact for more information?
Whom is she visiting?
“Whose” is used when asking about the possession of something.
Whose birthday is it?
Whose car are we taking?
“Why” is used when asking about the reason for something.
Why are you late? (What is the reason you are late?)
Why are they laughing? (What is the reason they are laughing?)
“Where” is used when asking about a location or a place.
Where are you going? (What place you are going to?)
Where is the new restaurant? (What is the place of the new restaurant?)
“How” is used when asking about the manner of things, but it is also used in combination with adjectives and adverbs.
How are you getting to work? (What is the manner with which you get to work?)
How do I do this? (What is the manner with which I do this?)
“How” can also be used with “much” and “many”, when asking about the quantity or the amount of something.
How much does this dress cost?
How many pieces of pizza did you eat?
“How” can also be used with adjectives or adverbs when asking about the intensity, the duration, the quality or the frequency or something.
How often do you go to the dentist?
How fast was he driving?
How are you?
How old are they?
How cold is it?
“Which” is used when asking about a choice between two things, or a selection of a known quantity of group. It is typically only used for things or objects, but not for people. We use “Who” for people.
Which bus do you take?
Which dentist do you go to?
Which one do you like better? The red one or the green one?
In many instances we can use “what” instead of “which“. “What” has a more general quality. “Which” is more specific. In some cases, they can be used interchangeably.
Which/What places did you go to?
Which/What classes are available this semester?
“What” is possibly the most frequently used, and most diverse question word. It is typically used when asking about things, general description or qualities, or activities.
What is the matter with you?
What color is the sun?
What is his favorite movie?
What did they do last weekend?
What does it look like?