Which, That, and Who

by Craig Shrives
The Quick Answer

Using "Which," "Who," and "That"

Use "which" for things and "who" for people. Use "that" for things and, informally, for people. For example:
  • The carpet which you bought has moth damage.
    • (A "carpet" is a thing, so "which" is correct. NB: Using "which" without a comma is unpopular, especially in the US.)
  • The carpet that you bought has moth damage.
    • ("That" can also be used to replace "which" without a comma. Using "that" (as opposed to "which" without a comma) is strongly preferred in the US.)
  • My Persian carpet, which I bought in Qom, has been chewed by the dog.
    • (A "carpet" is a thing, so "which" is correct. NB: Using "which" with a comma is fine.)
  • My Persian carpet, that I bought in Qom, has been chewed by the dog.
    • ("That" cannot be used to replace "which" with a comma.)
  • The boy who stole your bike is at the door.
    • (A "boy" is a person, so "who" is correct.)
  • The boy that stole your bike is at the door.
    • ("That" can also be used for people, but don't use it in formal writing.)

Using Commas with "Which" and "Who"

You never need a comma before "that." However, sometimes, you need a comma before "which" and "who." Here is the rule for using a comma before "which" and "who":

If the information added by the "who" or "which" clause is additional information (i.e., it's not essential to define another word), then offset the clause with commas.

For example:
  • Philosophy is written in the universe, which stands continually open to our gaze. (Philosopher Galileo)
    • (The clause "which stands continually open to our gaze" is just additional information. It does not define "the universe." Therefore, the commas are correct.)
Now look at this example:
  • Kindness is the language which the deaf can hear and the blind can see. (Author Mark Twain)
    • (The clause "which the deaf can hear and the blind can see" defines the word "language." Therefore, there are no commas.)
A "which" without commas can be replaced with "that." For example:
  • Kindness is the language that the deaf can hear and the blind can see.

Using "Which," "Who," and "That"

This page is about the relative pronouns "which," "who," and "that." They are used to head a clause (called a relative clause) that provides some information about another word in the sentence (usually the word immediately to the left). For example:

the relative pronouns who, which, and that

"Who" is used for people. "Which" is used for things, and "that" can be used for either. (Note, however, that using "that" for people is considered informal.) Here are some examples:
  • The man who punched the great white shark is on TV.
    • (The clause "who punched the great white shark" modifies "The man." As "The man" is a person, the clause starts with the relative pronoun "who." "That" could also have been used, but it might annoy some readers if used in a formal document.)
  • The PC which keeps breaking down is under guarantee until March.
    • (The clause "which keeps breaking down" modifies "The PC." As "The PC" is a thing, the clause starts with the relative pronoun "which." "That" could also have been used. In fact, "that" is preferable.)
  • The priest which was on the news last night used to be our local priest.
    • (A "vicar" is a person. Therefore, "who" should be used and not "which.")
  • Yesterday, the man who shot a swan in the park was jailed for 6 months.
    • (The clause "who shot a swan in the park" modifies "the man." As "the man" is a person, the clause starts with the relative pronoun "who." "That" is also an option for an informal document.)
  • Please accept my resignation. I don't want to belong to any club that will accept me as a member. (Comedian Groucho Marx)
    • (A "club" is a thing. Therefore, "which will accept me as a member" would have been acceptable. Note, however, that using "which" without a comma is not popular in the US.)

Commas with "Which" and "Who"

The biggest issue for native English speakers is knowing when to use a comma before "which" and "who." Unfortunately, the ruling is not simple. Look at this infographic:
when to use commas with which, that, and who

When "who" or "which" introduces a clause that is required to define the word it modifies, there are no commas, and the "who" or the "which" can be replaced by "that." If the "who" or "which" introduces additional information that is not essential to define the word it modifies, then the "who" or the "which" will be offset with commas and it cannot be replaced with "that."

Read more about using commas with "who" and "which."

Starting a Sentence with "Which" or "Who"

Do not start a sentence with words like "which" and "who" (unless it is a question).
  • Living in Scotland is cheaper than living in England. Which is lucky because I live in Dumfries.
  • If your garden is home to white plastic tables, gnomes, and a saggy washing line, be ashamed. You should view your space outside as an extra room. Which gives you a fantastic excuse to go shopping for lots of stuff to furnish it.

Whose and Who's

"Who's" is a contraction of either "who is" or "who has." It has no other uses.
  • Who's coming to fix the bed?
    • (who is)
  • Who's eaten the last muffin?
    • (who has)
  • I met the inspector who's delivering tomorrow's briefing.
    • (who is)
If you cannot substitute the "who's" in your sentence with either "who is" or "who has," then it is wrong and you should be using "whose."

Read more about "who's" and "whose."
Interactive Exercise
Here are three randomly selected questions from a larger exercise, which can be edited, printed to create an exercise worksheet, or sent via email to friends or students.

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See Also

Commas with which, that and who