英语语法：107 When to Leave Out "That"（在线收听）

Grammar Girl here.

Today's topic is the word “that.” When do you need it, and when can you leave it out?

Also, I'll have an announcement at the end of this show about extra book giveaways and my book tour.

Now, guest-writer Bonnie Trenga writes,

Today we’re going to talk about when it’s OK to omit the word “that” in a sentence. The sentences “The turkey sandwich I ate yesterday had too much mayonnaise” and “The turkey sandwich THAT I ate yesterday had too much mayonnaise” mean the same thing. In that sentence, it’s perfectly fine to leave out the “that.” In a similar vein, the sentences “I said I would eat a sandwich” and “I said THAT I would eat a sandwich” are equal. So are you allowed to leave out the “that” in such cases? Well, it depends.

"That" Can Help Sentence Flow

When you’re deciding whether to keep or omit your “that,” you need to consider how your sentence flows. Many times, it’s just a matter of personal preference. Some people think adding “that” improves the flow of the sentence and makes it easier for the reader to understand. Others believe they should delete every seemingly unnecessary “that” because they want to maintain an economy of words (1). I’m all for cutting unnecessary words, but I often like to keep my “that” if it helps the rhythm of the sentence. You’ll have to judge whether using “that” in your particular sentence improves or hurts its flow. Sometimes it helps to read your paragraph aloud to see if you’ve got the right rhythm. The AP Stylebook, which is typically used by journalists, suggests you use a “that” when in doubt (2). It advises, “Omission can hurt. Inclusion never does.”

Sometimes "That" Is Necessary

Now, there are several cases when a “that” might be necessary. If your sentence already has another “that” or two, you might not want to complicate it more by adding yet another “that” (3). One of the sentences above falls into this category. I said, “Some people think adding ‘that’ improves the flow of the sentence.” I could have also said, “Some people think THAT adding ‘that’ improves the flow of the sentence,” but I thought two cases of “that” would be a bit much.

Another time you should consider using a “that” is when your sentence could be ambiguous or misunderstood. Steven Pinker, a linguist, warns about what he calls “garden path sentences” (4). These are sentences that seem to mean one thing but then turn out to mean something else. Sometimes, keeping a “that” can help you avoid such problematic sentences. Pinker explains, “These are called garden path sentences, because their first words lead the listener ‘up the garden path’ to an incorrect analysis.”

Here an example of a sentence that leads the reader down the wrong path when you omit the word “that”:

Aardvark maintains Squiggly's yard is too big.

Without a “that,” the reader is initially led to believe that Aardvark maintains, as in mows, Squiggly's yard. If you add in a “that,” it's clear from the beginning that Aardvark just has an opinion.

Aardvark maintains that Squiggly's yard is too big (5).

Pinker goes on to say that garden path sentences are “one of the hallmarks of bad writing” because readers have to wend their way back to the beginning of the sentence to figure out its meaning.

It is sometimes tricky to know if your sentence is ambiguous because you, the writer, know what you mean. I always find it useful to put aside my work for a while and then read it again with fresh eyes. You could also consider having a friend or colleague read over your work.

Keep Parallel Construction

Two more points about “that” (6). First, be careful to maintain parallel construction. For example, this sentence is incorrect: “Natalie realized she had left her keys in the car and that she didn’t feed her fish.” In this sentence, Natalie is realizing two things, but the sentence uses only one “that.” This sentence would be better if you used “that” twice: “Natalie realized THAT she had left her keys in the car and THAT she didn’t feed her fish.”

Avoid the Double "That"

You also need to ensure you don’t accidentally put in a double “that.” This sentence is not right: “Natalie knows that if she doesn’t remember to feed her fish that the poor little guy will die.” It needs just one “that,” the first one: “Natalie knows THAT if she doesn’t remember to feed her fish, the poor little guy will die.” A comma after “fish” will help readers understand the sentence.

So, it's up to you to decide when you need a “that” to improve the flow of your sentence. Remember that some people prefer writing that omits unnecessary “thats,” but it's also more dangerous to leave them out because doing so can lead to misunderstandings.

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