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The Correct Use of That & Which

THAT and WHICH have several different functions within a sentence, but, in general, they are words used to introduce information in a sentence. One of the most common problems which occur with the use of THAT and WHICH concern their addition and deletion. Another problem concerns the use of THAT with essential information and the use of WHICH with non-essential information.

1. THAT MAY BE DELETED IF THERE IS NO DANGER OF MISREADING WITHOUT IT.
**EXAMPLE: I told Ed [that] I would be late.
**EXPLANATION: That can be deleted because the meaning is clear without it. This rule usually applies when that introduces additional information or a subordinate clause.

2.THAT IS NEEDED IF THERE IS A DANGER OF MISREADING WITHOUT IT.
**EXAMPLE: As Joe began to prepare dinner, he discovered that the oven wasn't working properly.
**EXPLANATION: Joe didn't discover the oven; he discovered that the oven wasn't working properly.

3.WHICH IS USED TO ADD NON-ESSENTIAL INFORMATION TO A SENTENCE.
**EXAMPLES: Ed's country house, which is located on thirteen acres, was completely furnished with bats in the rafters and mice in the kitchen.
**EXPLANATION: Since the phrase "is located on thirteen acres" is not essential to the meaning of the sentence, which is used.

If the phrase with which was placed at the end of the sentence, there would be a comma placed before it.
**Example: Chelsea likes Dalmations, which are white with black spots.

NOTE: Commas are used around or before this type of clause because the absence of the information would not change the main meaning of the sentence. (For more help, look up non-restrictive clauses and relative pronouns in a handbook.)

4. THAT IS USED TO ADD ESSENTIAL INFORMATION TO THE MEANING OF THE SENTENCE.
**EXAMPLE: For camp the children needed clothes that were washable.
**EXPLANATION: The clause "that were washable" is essential to tell what type of clothes the children needed; therefore, that is needed at the beginning of the clause.

**EXAMPLE: The corporation that hired my husband was hurt by recent budget cuts.
**EXPLANATION: The clause "that hired my husband" is essential to identify which corporation.

NOTE: Clauses that add vital information to a sentence do not need to be set off by commas. (For more help, read about restrictive clauses.)

5. THAT AND WHICH ARE NOT USED TO REFER TO PERSONS; INSTEAD, USE WHO OR WHOM.
**EXAMPLES: The fat man, who is my friend, died today.
Ex-fans wondered how and old man who walked with a limp could play football.
**EXPLANATION: In these examples, who must be used because these passages are about specific humans.

6. THAT OR WHICH MAY BE USED TO REFER TO A GROUP OR CLASS OF PEOPLE.
**EXAMPLES: The team that scores the most points in this game will win the tournament.
The Talking Heads, which broke up last year, is my favorite band.
**EXPLANATION: It is acceptable to refer to groups of people with that and which, but it is impolite to use that or which to refer to individuals.
When he heard about my child who lived at home, Gill smiled and said, "I would love to be a parent."

Final Note: IF you would like more help with your writing, please come by the CNU Writing Center or make an appointment.

Reference: Hacker, Diana and Wanda Van Goor. 2nd ed. Bedford Basics: A Workbook for Writers. Boston: Bedford Books of St. Martin's Press, 1994.

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