When to use “who” or “which”

“Who” vs. “Which”: What’s the difference?

Both “who” and “which” are considered interrogative pronouns or interrogative determiners. These are used to make asking questions simpler. Other common interrogative pronouns include “whom,” “whose,” and “what.”

For example:

• Who dropped off the flowers?
• Which car is yours?

Aside from asking questions, “who’ and “which” can be used as relative pronouns, which join two different clauses in a sentence.

Defining “who” and “which”

“Who” should always be used to refer to people. “Which” should be used to refer to things or inanimate objects. When it comes to animals, “who” is usually acceptable to use when referring to pets, while “which” should be used to refer to a species in general (for example, horses, dogs, and cats).

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It’s also important to note that “who” can be used for restrictive and non-restrictive clauses, while “which” is only used for non-restrictive clauses. Restrictive clauses are often necessary to identify someone or something about the noun in the sentence.

Meanwhile, non-restrictive clauses add extra information that can be removed from the sentence. The additional information in a non-restrictive clause is sectioned using commas. When a non-restrictive clause is removed from the sentence, the sentence will still make sense.

Here is an example of a restrictive clause:

• The student who won the award was John Smith.

The restrictive clause in the sentence above is ‘who won the award.’ Without this information, we would not know which student won the award. ‘Who’ is used in this sentence because it is referring to a person (John Smith).

Here are some examples of non-restrictive clauses:

• My husband, who is from New York, has a strong accent.

In the above sentence, if the non-restrictive clause was removed, it would be, “My husband has a strong accent.” The husband being from New York is not essential information. “Who” is used in this sentence because it refers to the husband.

• My laptop, which I only bought last year, is running low on storage.

In the above sentence, if the non-restrictive clause was removed, it would be, “My laptop is running low on storage.” The timeframe when the laptop was purchased is additional, unnecessary information. “Which” is used in this sentence since it is referring to an object (the laptop).

How to use “who” correctly in a sentence

Here are some more examples of how to use “who” correctly:

• His dog Coco, who was his first dog, had the loudest bark.

In the sentence above, the speaker is referring to a pet, so it is acceptable to use “who” in this case.

• Who made the reservation?

If you are wondering which person made a reservation, “who” is the correct word to raise this question.

• The doctor who did the surgery is new to the hospital.

In the above example, “who” is the correct word choice because the doctor is a person, not a thing.

“Which” used correctly in a sentence

Here are some examples of how to use “which” correctly:

• Which doctor performed the surgery?

In the above sentence, “which” is used as an interrogative determiner. In an interrogative determiner, ‘who’ cannot be used before a noun, so ‘which’ is the correct word choice here. “Which” may be used before a noun.

• Susan’s house, which is right on the water, was damaged by the hurricane.

The above sentence refers to a house, not a person, so “which” is the correct word to use.

• If you’re not sure which person to call, consult your manager.

In the above sentence, “which” is the correct word to use since it precedes a noun. To say “who person” would not make sense.

When in doubt, remember that ‘who’ is used to refer to people, while ‘which’ is used to refer to things. Aiming to further strengthen your grammar skills? Learn about the differences between parentheses and brackets, how to use parallelism to develop your writing voice, or when to use “that” or “which.”