Hello, ELA teachers! If your students could use a quick refresher on the most common grammar slip-ups, this post is a great place to start. Share it with your class to help them avoid easily fixable errors that every writer should know how to catch.

Most of the material here is adapted from our Maximum Impact and Grammar for Writing workbooks. Free sample pages are available to download for these programs.

Strong writers know there are certain grammar errors they should never make.

We’re not talking about messing up advanced grammar concepts like conditional sentences, adjective order, or subjunctive mood. No, these mistakes are so elementary and so obvious that anyone reading the text will immediately mark the writer as incompetent. And if the reader isn’t convinced that the writer knows what they’re doing, they probably won’t take anything the writer says seriously.

However, just as these grammar mistakes are easy to spot, they’re simple to correct—if you know the most basic rules of grammar. In today’s post, let’s take a look at some of the most common grammar offenses.

1. Run-on Sentences

For a sentence to be complete, it needs to have an independent clause and express a complete thought. Some sentences have more than one independent clause, but the clauses must be linked to make sense. Otherwise, you’ll create a run-on sentence.

For example:

I wanted to eat crab cakes my brother ordered a ribeye steak for me.
Independent clause + independent clause = run-on

There are two complete thoughts here. But they can’t exist in the same sentence as written. Instead, you can join them or change them completely.

You could use a comma and a conjunction, like this:

I wanted to eat crab cakes, but my brother ordered a ribeye steak for me.
Independent clause + , conjunction + independent clause = sentence

Or, you could rewrite the sentence entirely:

I wanted to eat crab cakes. My brother ordered a ribeye steak for me.
My brother ordered a ribeye steak for me even though he knew I wanted to eat crab cakes.
I wanted to eat crab cakes. However, my brother ordered a ribeye steak for me instead.

2. The Comma Splice

The comma splice is a type of run-on sentence. Here, a writer attempts to connect two independent clauses with only a comma. But that’s not enough to create a correct sentence.

We’re going to read The Great Gatsby, we’ll write a book report when we’re finished.
Independent clause , + independent clause = comma splice

The easiest way to correct this sentence is by adding a conjunction after the comma.

We’re going to read The Great Gatsby, and we’ll write a book report when we’re finished.
Independent clause + , conjunction + independent clause = sentence

You can also use a semicolon when fixing comma splices, but only if the independent clauses are closely related in thought.

Emily enjoys going to the mall; her favorite store is Sephora.
Independent clause ; + independent clause = sentence

3. Subject-Verb Agreement Mismatches

In order for a sentence to be grammatically correct, subjects and verbs must agree. What does that mean? The subject of a sentence must be in the same singular or plural form as the verb.

Incorrect: Three frogs was sitting by the pond.
Correct: Three frogs were sitting by the pond.

In the sentences above, the subject, frogs, is plural, so the verb, were, must also be plural.

4. Objective and Nominative Pronoun Mix-Ups

A pronoun is a word that stands in for a noun. There are two types of pronouns: nominative and objective. A nominative pronoun replaces the subject of a sentence, while an objective pronoun takes the place of the object.

Nominative pronouns: I, he, she, they, we
Objective pronouns: me, him, her, them, us

When it comes to sentences with multiple pronouns, people often mix up which type of pronoun they’re supposed to use. If you find yourself struggling, try to say the sentence without one of the pronouns. 

For example, consider this sentence:

Gordon took you and her to the restaurant.

If you remove you and from the sentence, you’ll get:

Gordon took her to the restaurant.

Her is the object of the verb took. You wouldn’t say, “Gordon took she to the restaurant.” The objective pronoun is correct.

5. Active and Passive Voice Problems

All English verbs are written in either active or passive voice. The active voice directly connects the verb with the subject. The passive voice puts the subject after the verb.

Active: She loves the cat.
Passive: The cat is loved by her.

Sometimes there’s no subject mentioned in passive voice sentences.

Passive: The cat is loved.

Strong writers avoid writing entirely in the passive voice. Why? First, the passive voice makes sentences longer. When the subject is last, you need to include a helping verb like is or was, and a preposition like by.

Active: The rabbit eats the carrot. 
Passive: The carrot is eaten by the rabbit.

The passive voice also makes the reader wait for the subject of the sentence.

Active: The pastry chef continues to create delicious cakes and cookies.
Passive: Delicious cakes and cookies continue to be created by the pastry chef.

Some writers also use the passive voice when they want to avoid responsibility for something, especially something negative, as they can leave off the subject completely.

Active: I broke the new TV.
Passive: The new TV was broken.

Writing in the passive voice isn’t necessarily incorrect. Good writers know how to use the passive voice sparingly for style, rhetoric, and dramatic flair. But if you don’t know how to apply the passive voice correctly, you might not get your point across clearly.

6. Using an Apostrophe to Make a Word Plural

Apostrophes can be tricky punctuation marks. They have two purposes: to show possession or ownership and to show that letters are missing from a word, as seen in contractions.

Possession

Auggie’s chew toy = a chew toy belonging to Auggie
The radio’s noise = the noise of a radio

Contractions

Should’ve = should have
Didn’t = did not

Many people think you can use an apostrophe to make a word plural, but that’s not correct—most of the time. You should use an apostrophe when you want to pluralize numbers and letters. But in all other situations, don’t do it.

Incorrect: five stick’s of gum; top song’s of the decade
Correct: five sticks of gum; top songs of the decade

Incorrect: scored As on the tests; many Chrysler 300s
Correct: scored A’s on the tests; many Chrysler 300’s

7. Dangling Prepositions

You might have heard that it’s wrong to end a sentence with a preposition. These are words like to, with, at, for, or about. In casual conversation or informal writing, it’s generally acceptable to use dangling prepositions sometimes. But when it comes to formal or academic writing, it’s better to avoid making this choice. Ending a sentence with a preposition can make your writing sound awkward or unclear.

Here’s an example of a dangling preposition:

That’s the topic I was talking about.

In informal circumstances, this sentence is fine. However, if you’re aiming for an elevated tone, you should change it. You can remove the dangling preposition by rewriting the sentence:

That’s the topic about which I was speaking.

The second version sounds more formal, which is great for academic writing. But if it’s too wordy for you, you can always rewrite the sentence entirely:

That’s the topic we discussed.

8. Misplaced Modifiers

Modifiers are words or phrases that share information about a part of a sentence. The general rule is that a modifier needs to be placed as close to the words it modifies as possible. If a modifier is in the wrong place, it can easily lead to confusion, as seen below.

I only ordered a large pizza from the shop.

The modifier in this sentence is only. The sentence means that the one thing I did was order a large pizza. But if we move the modifier around in the sentence, the overall meaning easily changes:

I ordered only a large pizza from the shop. (I did not order anything else.)
I ordered a large pizza from the only shop. (There is just one shop from which to order.)
Only I ordered a large pizza from the shop. (No one else ordered a pizza.)

Make sure you place the modifier exactly where it needs to be!

9. Number Versus Amount

Contrary to what many people think, in grammar, number and amount aren’t interchangeable terms. They each pair with different types of nouns. Use number with things you can count individually (count nouns). Use amount with things you can’t count easily (noncount nouns).

Incorrect: A large amount of students were absent. 
Correct: A large number of students were absent. (You can count students individually.)

Incorrect: A small number of water spilled.
Correct: A small amount of water spilled. (You can’t count water molecules easily.)

If you get confused when writing, think of it this way: If you can add an “s” at the end of the noun (like books, pencils, candies), use number. If the noun stays the same in singular and plural (like light, time, information), use amount.

10. Commonly Confused Words

Some words in English look or sound alike but have completely different meanings. Mixing them up can lead to baffling or incorrect writing.

It’s vs. Its

The word it’s is a contraction of “it is” or “it has.”

It’s a beautiful day. (It is a beautiful day.)
I think it’s been a great event. (I think it has been a great event.)

Its is a possessive pronoun like his or her. You use its to show ownership of something.

The bird flapped its wings. (The wings belong to the bird.)
The lamp cast its light on her face. (The light belongs to the lamp.)

If you ever get confused between the two, here’s a simple trick: If you can replace the word with “it is” or “it has,” use it’s. If not, use its.

Your and You’re

The word your means “belonging to you.” 

Your dog chewed on my shoes. (The dog belongs to you.)
It’s your problem now. (The problem belongs to you.)

Conversely, the word you’re is a contraction of “you are.” 

You’re the most intelligent person I know. (You are the most intelligent person I know.)
Everyone knows you’re reliable. (Everyone knows you are reliable.)

They’re, There, and Their

The word there has two uses. The first is as an adverb that indicates place or location. 

He is standing right there.
I need you to move over there.

There also begins certain clauses and sentences.

There might be a way to fix this.
I need to know if there is anything else I need to do.

They’re is a contraction of “they are.”

I heard they’re looking for a new doctor. (I heard they are looking for a new doctor.)
They’re always talking about the latest movies. (They are always talking about the latest movies.)

Their is a possessive pronoun meaning “belonging to them.”

Their flight was cancelled because of the storm. (The flight belongs to them.)
George and John decided to drive their SUV to the beach. (The SUV belongs to George and John.)

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