“who” vs. “which”

Use "who" to refer to people (and sometimes personified animals); use "which" to refer to things, ideas, or animals/groups discussed impersonally.

The real distinction

The core distinction is straightforward: "who" refers to people, while "which" refers to things, animals, or ideas, and using "which" to refer to a specific individual person ("the man which called") is considered a clear grammatical error in standard English, just as using "who" for an inanimate object ("the car who broke down") would be incorrect. The distinction becomes slightly less clear-cut with animals, where "who" is often used for pets or animals with names and personalities ("the dog who greeted us at the door"), reflecting a sense of individual personhood, while "which" remains standard for animals discussed more generically or scientifically ("the species which inhabits this region"). Collective nouns referring to groups of people, such as "team," "committee," or "family," can sometimes take "which" when the group is being treated as a single unit rather than a collection of individuals ("the committee, which meets monthly, approved the budget"), though "who" is also acceptable and often preferred when emphasizing the human members. As a reliable default: reserve "who" strictly for individual people (and personified animals), and use "which" for objects, abstract concepts, and animals or groups discussed impersonally.

Examples with “who”

• The scientist who discovered the vaccine won a Nobel Prize.
• Who left this note on my desk?
• She's the one who suggested the idea in the first place.
• The teacher who inspired me the most retired last year.
• Who is responsible for organizing the event?
• He's the author who wrote that bestselling novel.
• The woman who answered the door seemed confused.
• Who called during the meeting this morning?
• The nurse who treated him remembered his name years later.
• She's the friend who always knows what to say.
• Who wrote this beautifully detailed letter?
• Who designed the elaborate float for the parade?
• Who first suggested moving the deadline up a week?
• Who volunteered to organize the neighborhood cleanup?

Examples with “which”

• Which restaurant should we choose for dinner tonight?
• The car, which was brand new, broke down within a week.
• Which of these options do you prefer?
• The novel, which took years to write, became a bestseller.
• Which route is faster during rush hour?
• The committee, which meets monthly, approved the new policy.
• Which laptop has the better battery life?
• The painting, which hung in the museum for decades, was finally sold.
• Which flavor of cake would you like for the party?
• The species, which inhabits only this region, is now endangered.
• Which of the two candidates addressed the issue more directly?
• Which streaming service offers the better selection of documentaries?
• Which neighborhood has the shortest commute to downtown?
• Which brand of coffee do most reviewers recommend?

Memory trick

Remember "who" always points to a person, just like "he" and "she" — all three words are about human identity. "Which" points to things or choices among options, sharing its root with the impersonal question words used for objects rather than people. As a last check, try substituting "he" or "she" for the word — if that works, you need "who"; if instead "it" fits better, you need "which."