Who, That, and Which
This article clarifies the distinctions between "who," "that," and "which," and how to choose between them. Keep reading to learn the parts of speech, pronunciation, and accepted US usage of the words "who," "that," and "which."
Who is a pronoun; that is a pronoun, adjective, adverb, and conjunction; and which is a pronoun and adjective. Of all these uses, the one in which they are mistaken, one for the other, is when they are used as relative pronouns. Let’s look at how each of them works and the situations in which it is proper to use one rather than the others.
Who, pronounced /HOO/, is a pronoun that can be used as both an interrogative pronoun and a relative pronoun. As a relative pronoun, it introduces a clause in cases in which the antecedent (what is modified by the clause) is one or more persons, or something to which personality is ascribed, like a character in a book, film, or television show; a pet; or something else that is personified. Some experts feel that the use of who should be restricted to references to people. Here are example sentences:
Person: It must have been my daughter who called you, because it certainly wasn’t me.
Character: The Scarecrow, who was stuck on a pole when Dorothy first met him, proved to be a loyal friend.
Pet: It’s John’s other cat, Snickers, who walks along the piano keys, “playing” the piano.
Other: In the story about the contest between the Sun and the Wind, the Sun, who took a gentler approach than the Wind, was much more effective in getting the man to take off his coat.
That, pronounced /THAT/, is a pronoun that can be used as a predicate nominative, the object of a preposition, or the subject of a sentence. It can also be used as a relative pronoun to introduce a clause. That’s where agreement ends. What that can refer to and what kind(s) of clause it can introduce are matters of debate. Let’s begin to clarify the situation by looking back at who.
The first example for who demonstrates who used to introduce a restrictive clause, one that defines what is being talked about, as opposed to a nonrestrictive clause, as in the final sentence which adds information but is not needed to indicate which “Sun” we’re talking about (there’s only one). Some experts think that who, but not that, should be used when the referent is a person. Others think that using them interchangeably is a) descriptive of actual language and b) not a problem. This would mean that this example would be fine:
Person: It must have been my daughter that called you, because it certainly wasn’t me.
My own opinion is that - given that we have two words and can easily make a distinction that makes it easier for listeners and readers to identify the referent, why not use it for clarity?
The use of that that is not debated is its use introducing a restricted clause referring to a thing, like this:
The soccer ball that is in the backseat of my car is the one I want.
Note that sometimes people omit the that at the beginning of such clauses and say:
The soccer ball in the backseat of my car is the one I want.
Which, pronounced either /HWIHCH/ or /WIHCH/, is an interrogative pronoun, as well as a relative pronoun that can be used after that or a preposition
I freely share that which is mine.
The creed in which I believe gives me strength.
or as a relative pronoun to introduce a clause that gives additional information about the antecedent
The olives in my salad, which is very tasty by the way, have pits.
These uses are agreed upon. A question arises, however, of whether it is appropriate to use which to introduce restrictive clauses as well as nonrestrictive clauses. This is common practice in British English:
The shoe which the horse lost is gone for good.
In US usage, however, it is a matter of some debate, with some saying that writers especially should distinguish restrictive clauses by using that and nonrestrictive clauses by using which. My point, as above is: if we have, built into our language at this point, a way to make a distinction and make it clearer to an audience what meaning is intended, why not use it?