Your writing has an underlying tone, and grammar mistakes can reveal that tone. Even skilled content writers may make these errors if they’re not careful.
One of the most common grammatical mistakes is swapping that and which in relative clauses. That’s not surprising, since these two words overlap in meaning and the rules differ slightly.
Which is a Restrictive Clause
Since the mid-17th century, when this debate began, the rules of which and that have become fairly clear. You should use which to introduce a nonrestrictive clause, and that for restrictive ones. This is not a strict rule, however, and skilled authors can occasionally break it if the resulting prose sounds more natural.
If a clause is essential to the meaning of a sentence, it should be introduced with that. For example, if you want to know which shirt of John’s to clean for the wedding, you should use that. However, if the information isn’t vital to the meaning of the sentence, it can be introduced by which. These are referred to as nonessential clauses, and they’re usually offset with commas. For example, if you’re talking about the gym that’s five minutes away from your house, you would use which to specify the one with the racquetball courts. But be careful not to overuse which; if it becomes unnecessary, the reader may be confused by your use of it.
Which is a Nonrestrictive Clause
As far as grammar rules go, the difference between which and that may not be the most contentious. But it can still trip up writers. Fortunately, knowing when to use each can make writing easier and more accurate.
A nonrestrictive clause contains extra or nonessential information and is usually set off with commas. It describes a noun in a way that does not limit or identify it as essential to the meaning of a sentence. The bucket that has apples in it is blue.
A restrictive clause is the opposite of a nonrestrictive clause. It limits or identifies a noun or pronoun as essential to the meaning of a sentence. It should take the relative pronoun that. The children need sturdy shoes for camp. The bucket that has apples in it is expensive.
Which is a Question
One of the quickest hacks for deciding whether to use which or that is to test your sentence with a question mark. If the clause that you’re considering eliminating changes the meaning of your sentence, use which; otherwise, use what.
Changing which to that can also help clarify the antecedent. For example, “What of your shirts are you considering for the photo?” sounds better than “Which shirts are you considering for the photo?”
Remember that in tag questions (questions that introduce another sentence with a do-verb) you use the opposite form of the verb used in the tagged sentence to construct the question mark: “Isn’t it true that…”
Which is a Subordinate Clause
The word which, along with words like who, whose, whomever, and which, begin relative dependent clauses. A dependent clause can’t stand on its own and depends on an independent clause to form a complete sentence. These clauses are also called adverbial clauses or subordinating conjunctions. They can be a tricky part of grammar to master.
If you don’t follow the rules on using which, you could make a mistake that affects the overall meaning of your sentence. It’s important to remember that which is used to introduce restrictive clauses, while who is used to introduce nonrestrictive clauses. Knowing these rules can help you avoid confusion when writing about people and other living things. It’s also helpful to know that which and who aren’t interchangeable when describing inanimate objects or other non-living things. Those are the kinds of cases where a comma is required before and after the relative pronoun.