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More Common Grammar Mistakes

A couple of months ago, I posted a blog about the three most common grammar issues I see in my editing work. Today I am going to discuss three more errors that show up frequently in the books I edit.

Misuse of “That” and “Which” in Adjective Clauses

Many people use “that” and “which” interchangeably to introduce an adjective clause, but they actually have different purposes. “That” should be used with a restrictive clause, while “which” is used for nonrestrictive clauses. I can hear you all saying, “Gee, thanks. That clears it all up.” A restrictive clause is simply one that provides information that is vital to the understanding of the sentence. A nonrestrictive clause may provide information that is helpful or informative, but without it, we’d still know what we needed to. Here are a few examples:

Restrictive clause: The car that hit me last night was totaled.

In this sentence, “that hit me last night” tell us the specific car we are discussing. Without it, the sentence would say, “The car was totaled.” There is not enough information here for us to know which car in particular the writer means, so the clause is restrictive and uses “that.” Note that we do not use commas around restrictive clauses.

In contrast, here we have a similar sentence with a nonrestrictive clause: My car, which was rear-ended last night, is in the shop.

In this case, the sentence says “my car,” so we already know which car we’re discussing before we get to the adjective clause. While the clause “which was rear-ended last night” gives us useful information, we would still know which car the writer was referring to without it, so this is a nonrestrictive clause and uses “which.” Nonrestrictive clauses are set off with commas.

Here are two more examples:

Restrictive clause: The dog that bit me didn’t have rabies, thank goodness.

Nonrestrictive clause: My sister’s dog, which bit the neighbor’s son, didn’t have rabies, thank goodness.

Misuse of Commas around Names Used as Appositives

This is similar to the topic above in that it, too, hinges on whether the name in question is restrictive or nonrestrictive. First a definition. An appositive is simply a noun that follows another noun our pronoun to identify or explain it. If the appositive is restrictive, is provides information that is essential to establishing the meaning of the noun. If it is nonrestrictive, it gives us added information, but is not necessary for defining the noun. Consider the examples below.

Restrictive appositive: My friend Sandy is a fantastic illustrator. The name “Sandy” here is being used as an appositive to identify the noun “friend.” Most people have more than one friend, and it is safe to assume the writer here does, as well. If we were to remove the name “Sandy” here, we would not know which of the author’s friends is a fantastic illustrator so it is restrictive and no commas are used.

Nonrestrictive appositive: My best friend, Sandy, is a fantastic illustrator. In this instance, since we’ve specified “best friend,” we have changed “Sandy” to a nonrestrictive appositive. By definition, you can only have one best friend, so even without the name, we would know who the writer was referring to. Again, the name “Sandy” gives us useful information, but it is not information that is essential to establishing which friend is the fantastic illustrator. Because it is nonrestrictive, the name is surrounded by commas.

Let’s consider another example.

Restrictive clause: My sister Jenny is an English teacher. (Assuming the writer has more than one sister.)

Nonrestrictive clause: My twin sister, Jenny, is an English teacher.

(A side note: if the writer only had one sister, then the first sentence would be become “My sister, Jenny, is an English teacher” because if there is only one sister, then there is no question who “my sister” is.)

Comma Splice

A comma splice is a type of run-on sentence that uses a comma to join one independent clause (a clause that can stand on its own) to another.

For example: My family has a game night every Tuesday, we have so much fun together.

We have two independent clauses here—“My family has a game night every Tuesday” and “We have so much fun together”—and a comma is not a strong enough punctuation mark to separate them. This sentence could be fixed in one of several ways.

Make it two sentences: My family has a game night every Tuesday. We have so much fun together.

Add a conjunction: My family has a game night every Tuesday, and we have so much fun together.

Add a semicolon (if the two clauses are closely related): My family has a game night every Tuesday; we have so much fun together.

Sometimes comma splices are used on purpose for effect to create a casual feel or a sense of breathless stream of consciousness, but not everyone agrees that it is acceptable. Unless you have a good grasp on why comma splices are typically considered errors and are using them to create a specific effect, you are better off steering clear of them and rewriting your sentence.

Do you have trouble with any of these common errors? Are there other errors you’d like me to address in future posts? Leave a comment below and let me know!

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