One of the trickier grammar rules in the English language is the difference between the words that and which. Both serve a similar purpose of clarifying the information in a sentence. As you develop your business writing skills, using each word correctly will strengthen your communication. Today, we'll discuss when to use that and which.
Let’s start with the similarities between these words (and some background information).
That and which both introduce adjective clauses. A clause is any group of words that includes a noun and a verb. There are independent clauses (full sentences such as “I like to eat ice cream”) and dependent clauses (incomplete sentences that do not express a complete idea, such as “When I get to school …”)
Adjective clauses are dependent clauses that describe nouns, i.e. they act like adjectives. However, in English, adjectives come before the noun and adjective clauses come after the noun. Adjective clauses often start with the words who, whom, whose, where, when, which, and that. Here is an example of each (the adjective clauses are underlined):
ACME Biochemical is one of the places where I want to work.
“Where I want to work” describes places.
Tom Jones is the man whose dog attacked me.
“Whose dog attacked me” describes the man.
John and Sarah are the people whom I would like to work with on this project.
“Whom I would like to work with” describes the people.
Divisions that generate profit often glean admiration.
“That generate profit” describes divisions.
Shinzo Abe, who was Japan’s longest-serving prime minister, was assassinated in July 2022.
“Who was Japan’s longest-serving prime minister” describes Shinzo Abe.
We should all pay attention to David’s new product idea, which is likely to triple sales next year.
“Which is likely to triple sales next year” describes David’s new product idea.
Look at the examples again. Do you notice something different about the last two examples? The punctuation is different; the adjective clause is contained within commas. This gives you a hint at the difference between which and that, and how to use that or which correctly.
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View all of our coursesTheir difference is that one is used to present essential information in the sentence and the other is used to present non-essential information in the sentence.
Let's dive deeper into this challenging grammar concept, and how you can immediately determine the correct answer for that or which every time you construct a sentence.
Below is the correct usage of that:
Divisions that generate profit often glean admiration.
The words that generate profit restrict the divisions you're talking about. Without this restrictive clause of the specific divisions, the meaning of the sentence would change. Without clarification, you'd be stating that all divisions glean admiration, not just the profitable divisions.
The clause “that generate profit” is essential to the meaning of the sentence, so the correct word is that. You cannot remove that clause without changing the meaning of the sentence. Also, a comma is never needed with that in a restrictive clause.
Here's the correct usage of which:
We should all pay attention to David’s new product idea, which is likely to triple sales next year.
The clause following which is likely to triple sales next year adds extra information to the sentence. They are nonrestrictive, which means that you can remove them and the sentence will still have the same meaning. “David’s new product idea” is clear and specific enough without the which clause, so it's a nonrestrictive clause/nonessential clause. And when you don’t need the information in the adjective clause, you do need the commas.
A comma is never needed with that in a restrictive clause. But in the case of which, you always need the commas. This is confusing, but I always remember it as an inverse relationship:
If you NEED the information, you DON’T NEED the commas. That introduces necessary information. You need the information for the sentence to make sense, so you do not need the commas.
If you DON’T NEED the information, you NEED the commas. Commas set off extra, unnecessary information. Which is always used with commas in an adjective clause.
**These punctuation rules apply to the other adjective clauses as well - those that start with who, whom, when, where, and whose. If you need the info, don’t use commas. If it’s extra info, make sure to use those commas!
Quick review time! Remember these key ideas to help you choose that or which and use them correctly:
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