1.
what one?: Which of these do you want? Which do you want?
2.
whichever: Choose which appeals to you.
3.
(used relatively in restrictive and nonrestrictive clauses to represent a specified antecedent): The book, which I read last night, was exciting. The socialism which Owen preached was unpalatable to many. The lawyer represented five families, of which the Costello family was the largest.
4.
(used relatively in restrictive clauses having that as the antecedent): Damaged goods constituted part of that which was sold at the auction.
5.
(used after a preposition to represent a specified antecedent): the horse on which I rode.
6.
(used relatively to represent a specified or implied antecedent) the one that; a particular one that: You may choose which you like.
7.
(used in parenthetic clauses) the thing or fact that: He hung around for hours and, which was worse, kept me from doing my work.
8.
Nonstandard . who or whom: a friend which helped me move; the lawyer which you hired.

–adjective
9.
what one of (a certain number or group mentioned or implied)?: Which book do you want?
10.
whichever; any that: Go which way you please, you'll end up here.
11.
being previously mentioned: It stormed all day, during which time the ship broke up.

more about which:

— determiner
1. a. used with a noun in requesting that its referent be further specified, identified, or distinguished from the other members of a class: which house did you want to buy?
b. ( as pronoun ): which did you find?
c. ( used in indirect questions ): I wondered which apples were cheaper

2. a. whatever of a class; whichever: bring which car you want
b. ( as pronoun ): choose which of the cars suit you

3. used in relative clauses with inanimate antecedents: the house, which is old, is in poor repair

4. as; and that: used in relative clauses with verb phrases or sentences as their antecedents: he died of cancer, which is what I predicted

5. archaic the which a longer form of which, often used as a sentence connector

1

Remember that “which” and “that” are primarily used as relative pronouns, words that relate to another noun preceding it in a sentence. For example: The house that Kathy purchased needs work. In this sentence, the relative pronoun “that” refers back to the noun, “house.” The senator voted for Proposition 21, which gives parents the right to choose their child’s school. In this sentence, “which” relates to Proposition 21.

2

Use “that” in a restrictive clause. A restrictive clause is critical to understanding the main clause (or the main part of the sentence). In the earlier examples, the clause “that Kathy purchased” is restrictive because without it, the noun “house” would not have the same meaning.

3

Use "which" in a nonrestrictive clause--a clause that, if deleted, would not change the essential meaning of the sentence. Study the second example, and you’ll see “which gives parents…” is a nonrestrictive clause because it is not critical to understanding the sentence. In other words, it’s an additional explanation that simply helps to define further the noun, "Proposition 21."

4

Remember : “which” and “that” refer only to nouns that are things. Whenever referring to people, you would use the relative pronoun “who.”

Who knew that two little words in the English language could be so vexing? "That" and "which" may seem interchangeable, but the truth is that each has a unique role in composition. Ask anyone when to use each one, however, and you'll get a different answer every time. Although using that or which incorrectly will not--in most cases--muddle your meaning, knowing how to use it correctly will make your writing sophisticated and relentlessly clear. Read on to learn how to use that/which.

Instructions

1

Use "that" to introduce a "restrictive clause." A restrictive phrase, as its name suggests, restricts the meaning of the person or thing that came before it--in other words, it specifically identifies who or what you're talking about. Take a look at this sentence: "I'd like an avocado that is not too ripe." The restrictive clause here, "that is not too ripe," is essential to the sentence's meaning. If you remove it, the meaning changes and loses specificity.

2

Use "which" to introduce a "nonrestrictive clause." A nonrestrictive clause describes the person or thing you're discussing, but it is not essential to the meaning of your sentence. You should be able to remove the "which" clause without altering the meaning. For example: "I like avocados, which have a buttery, nutty taste." If you take out the "which" clause, the meaning of this sentence remains the same--the speaker still likes avocados just as much as she did before.

3

Understand the punctuation that accompanies that or which. When you use "that," you generally do not use a comma before it: "The dog that I loved the most was a poodle." You should generally use a comma before "which": "Our poodle, which lived to be 16, was the best pet I've ever had." Or, "Our poodle lived for 16 years, which is a long time for a small dog."

4

Understand that this grammar issue can be a very important matter--this isn't just nit-picking. For example, consider these two sentences: "I love cats that don't scratch rowdy children." "I love cats, which don't scratch rowdy children." Unless this speaker has grown up with super-docile cats, he needs to use "that." Why? Because "that don't scratch rowdy children" identifies the kind of cats he loves. You can't remove the clause from the sentence and retain the sentence's meaning. The second sentence is incorrect for two reasons. First, many cats do scratch rowdy children; the clause "which don't scratch rowdy children" suggests otherwise. Second, the meaning of the sentence changes if you take out the clause: "I love cats" implies that the speaker likes all cats, when the truth is that she likes only those cats that do not scratch children. A vital meaning of the sentence is at stake here, and it's imperative to use that/which properly.

5

Test your usage of that/which when you revise your work by asking yourself these questions: If I take out the clause, does my sentence's meaning remain the same? If it does, you should use "which." If the meaning changes, use "that." Does the sentence call naturally for a comma? If it does, this might be a signal that you need to use "which."