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Common Grammar Mistakes

Common grammar mistakes include comma errors, apostrophe errors, sentence fragments, run-on sentences, and misplaced modifiers. All of these errors cause unclear and grammatically incorrect writing.

Commas

Comma splices are very common and result in run-on sentences.

I have to run to the store, then I am going to the gym to workout.

To fix this error, the writer must add a connecting word, a semi-colon, or add a period and make a separate sentence:

I have to run to the store, and then I am going to the gym to workout.
I have to run to the store; then I am going to the gym to workout.
I have to run to the store. Then, I am going to the gym to workout.

Another comma error can be found on Facebook. When posting a birthday message, the proper format is:

Happy Birthday, Ralph!

A comma should be placed between the person's name and the message because one is addressing that person directly.

Apostrophes

Apostrophe errors are also common. Apostrophes are used to show possession, to show that certain words are plural, and to show that letters are missing.

Apostrophes show possession:

Jim's coat (singular possession)
The children's clothes (possession for plural noun that does not end in s)
The dogs' toys (possession for plural nouns that end in s)
Jim and Ted's apartment (possession shown on the last noun)

Apostrophes are also used in contractions to show missing letters and numbers:

Can't (cannot)
I'm (I am)
Who's (Who is)
‘70 (1970)

Also, when writing the ‘70s, no apostrophe is present after the number when no possession is being shown.

Sentences

Sentence fragments are another common grammar error:

Fragment: Because I wanted the ball.
Sentence: Because I wanted the ball, I ran down the hill.
Sentence: I ran down the hill because I wanted the ball. (Notice that no comma comes before because when the phrase is within the sentence).

Fragment: Or take the car.
Sentence: Take the train or take the car.

Run-on sentences are a serious problem in college writing classes:

Run-on: I went to the park to run Sarah was there so I talked with her for a little while and we went to have some lunch.
Correction: I went to the park to run. Sarah was there, so I talked with her for a little while, and we went to have some lunch.

Possession

Misplaced modifiers are also very common grammar mistakes:

Incorrect: The girl smiled at the camera holding the basket of fruit. (The camera was holding the basket of fruit?)
Correct: Holding the basket of fruit, the girl smiled at the camera.

Choosing the Correct Form of the Word

There: a place
Their: a possession
They're: They are

Whose: related to a possession
Who's: who is

To: a direction
Too: also

Two: a number