The 10 Most Common Grammar Mistakes
  • 9-minute read
  • 3rd February 2023

The 10 Most Common Grammar Mistakes

Whether you’re learning English online or in person, you’ve likely experienced trouble with grammar at some point. As a student, it can be frustrating when your teacher highlights grammatical errors in your writing (often without indicating why they’re errors).

In this post, we’ve compiled 10 common grammar errors in English with explanations and examples to help you avoid them in your writing. Believe it or not, even native English speakers unwittingly make these mistakes! By being aware of these errors, you’ll know what to watch out for, and your writing skills will improve.

1.   Subject-verb Agreement

This is a common mistake associated with grammar tenses, in which the subject doesn’t agree with the corresponding verb. Let’s consider this example:

The mayor (subject) sign (verb) the contract.
The mayor signs the contract.

The mayor is an example of a third-person subject (e.g., he, she, it, they). Since this is in the present simple tense, the verb must be conjugated as signs to agree with the subject.

Subject–verb agreement errors often occur with collective nouns (e.g., family, audience, group) and infinitive nouns (e.g., anybody, everybody, none). Because these nouns appear to be more than one person, the writer erroneously assumes the verb shouldn’t be conjugated as the third person. You can avoid this type of error by:

●  Knowing which subjects are singular and plural

●  Making the verb agree with the closer subject when or, nor, either/or, or neither/nor connects two subjects

●  Watching out for subject complements (don’t confuse the subject complement for the real subject of a sentence)

Additionally, make sure you’re looking at the correct subject. Look at this example:

The writing (noun) in those paragraphs (noun) is (verb) horrible.

Because paragraphs is the last noun before the verb, it can be tempting to assume it’s the subject. However, it’s actually the object of a preposition (in). Therefore, writing is the correct subject of this sentence.

2.   Pronoun-antecedent Agreement

This occurs when a pronoun doesn’t agree with the noun it’s referring to (the antecedent).


The dog wagged their tail.
The dog wagged its tail.

Students and writers often don’t know which pronoun to use with animals, so they erroneously use plural pronouns, such as their, like in the above example. The straightforward rule is that singular and plural nouns must go with their respective singular and plural pronouns. An example of this error would be:

Each boy must sign in when they arrive.

Boy is singular, and they is plural. Therefore, the correct version would be:

Each boy must sign in when he arrives.

You can avoid this error by knowing which pronouns are singular and plural. Indefinite pronouns (everybody, nobody, somebody, etc.) are often mistaken as plural when they’re actually considered singular. When compound antecedents are joined by and, both nouns become plural (e.g., Jack and Jill).

You should also be careful with compound antecedents that are joined by or, nor, either/or, or neither/nor. The pronoun should agree with the closer antecedent.

Example: Neither the nurse nor the doctors like when their patients are in pain.

3.   Run-on Sentences and Comma Splices

Run-on sentences and comma splices occur when two independent clauses are incorrectly joined. Either a comma is missing, or it needs to have a conjunction after it in a sentence. Let’s consider this example of a run-on sentence:

The dog is sleeping on the bed it looks very comfortable.

As you can see, the sentence is missing a comma and is difficult to read. We would add a comma and a conjunction to improve readability:

The dog is sleeping on the bed, and it looks very comfortable.

Here’s an example of a comma splice:

The cat is sleeping on the bed, it looks very comfortable.

Again, this doesn’t read well. To correct it, you could change the comma to a semicolon or add and after it.

The cat is sleeping on the bed; it looks very comfortable.
The cat is sleeping on the bed, and it looks very comfortable.

To avoid run-on sentences, see if two or more independent clauses communicate more than one idea. If there is more than one idea, you must add a comma. Similarly, you can solve comma splice errors by:

●  Adding a conjunction

●  Changing the comma to a semicolon

●  Making separate sentences if necessary

4.   Misplaced and Dangling Modifiers

Modifiers add spice to sentences and descriptive speech. You can use modifiers in the form of adjectives or adverbs. For example, you can modify the word lion by adding an adjective: the fearsome lion or the powerful lion.

Modifiers need to be placed very close to the word they’re modifying. Unfortunately, writers sometimes misplace the modifiers by placing them too far away from the words they’re meant to connect with, thus changing the sentence’s meaning. Let’s consider an example of a misplaced modifier:

She almost (modifier) walked for the entire day.

It’s not clear which word is being modified. Did she crawl for the day? Did she walk slowly? Had she thought about walking for an entire day but decided against it? We don’t know. However, if we move the modifier, we can change the sentence to match the writer’s intended meaning:

She walked for almost the entire day.

Now, we get it! She did walk, and she walked for nearly an entire day.

Dangling modifiers occur when something modifies a word or phrase that hasn’t been identified. Let’s take this example:

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Looking into the distance (modifier), the sun dipped below the horizon.

Was the sun looking into the distance? That’s unlikely, unless it was one of those smiling cartoon suns. So, who was looking into the distance? To clarify, we should add the word being modified.

As Tom was looking into the distance, the sun dipped below the horizon.

Much better! Now we know who was looking into the distance.

To avoid misplaced modifiers, you need to know the word or phrase you’re trying to modify and place the modifier very close to the intended word. With dangling modifiers, you always need to clarify what’s being modified. You can also rephrase the sentence so that it’s clear.

5.   Homophone Trouble

Homophones are words that sound the same but have different spellings and meanings. They’re also often spelled similarly, which makes them easy to confuse in writing. Take your and you’re. The former is a possessive adjective, while the latter is a contraction of you are. However, it’s easy to get them mixed up. Here are a few examples of using your and you’re:

Your the most beautiful woman I’ve ever seen!.
You’re the most beautiful woman I’ve ever seen!
I like you’re shoes!
I like your shoes!

Another common homophone error is there, they’re, and their. Take these examples:

Their going to be here tomorrow.
They’re going to be here tomorrow.
They’re is a lovely beach to visit in my town.
There is a lovely beach to visit in my town.
Do we know there address?
Do we know their address?

Homophone errors might not matter when speaking, but they do in writing! So, it’s vital to know the differences between the meaning of those mentioned above:

●  There describes a location (i.e., the opposite of here).

●  They’re is the shortened version of they are.

●  Their is the possessive form of they.

When working with homophones, take a moment to think about which word is correct by going through the different meanings of each spelling. This can be tedious at first, but with practice, it’ll become second nature.

6.   Adjective and Adverb Confusion

Confusing adjectives and adverbs results in writing that comes off as very informal or uneducated. You’ll often notice this issue with words ending in “-ly.” Let’s look at these examples:

I’ve worked real hard to plan this trip.
I ran quick to the train station.

This is what the writer actually meant:

I’ve worked really hard to plan this trip.
I ran quickly to the train station.

To avoid such errors, you should know which word the adjective or adverb in question modifies. If the word modified is a noun or pronoun, use an adjective. If it’s a verb, also use an adjective. And if it’s an adverb, use an adverb.

7.   Overusing Adverbs

Writers tend to overuse adverbs, especially fiction authors. Adverbs are often overused to describe actions and events. Here’s an example from a work of fiction:

The curtain opened quickly, and Ben came slowly into the room. He saw Emma looking angrily at him. “Where have you been?” she asked furiously.

Because of the overabundance of adverbs, there’s more telling than showing. We could rephrase the passage with fewer adverbs to provide more kick:

The curtain flew open, and Ben entered the room. Emma was glaring at him. “Where have you been?” she demanded.

See the difference? The new words carry the same meaning, but there’s more show than tell (paramount for fiction writers).

You can avoid this error by using adverbs sparingly, especially when describing actions and events. Think of different verbs that will convey the same meaning.

8.   Misplaced Apostrophes

Apostrophes can indicate that something belongs to someone or something else. For example:

The girl’s sheep.

Writers sometimes misplace apostrophes with regular plural nouns when describing what or who they belong to. For example:

Where are the dogs’s owners?
Where are the dogs’ owners?

Another misplaced apostrophe error occurs with it’s and its. For example:

The lion roared, and I saw it’s
The lion roared, and I saw its teeth.

Remember that it’s is short for it is. So, there’s no apostrophe at the end of its when it’s being used as a possessive. You should also remember to place the apostrophe at the end of regular plural nouns.

9.   Incomplete Comparisons

Comparisons compare one noun to another by using comparatives. The error occurs when a comparison is left incomplete. Take this example:

It was much hotter today.

The reader will respond, “It was much hotter than when?” We need to complete the comparison in this sentence. Here’s one way:

It was much hotter today than yesterday.

When using comparisons, be sure to complete them. We can’t have comparisons if we don’t know who or what they’re being compared to.

10.             Mixed Verb Tenses

This is a form of faulty parallelism in which there are mixed verbs within a sentence. Take this example:

Lori takes a running start and jumped over the wall.

This sentence is unclear because it contains a verb in the present and past. Therefore, both verbs need to be in the same tense for consistency.

Lori took a running start and jumped over the wall.

To avoid this error, remember to have consistency in verb tense. Determine if your sentence is referring to the past, present, or future, and then make sure all your verbs match that.


These are just a few examples of common grammar mistakes, but there are many other mistakes that people make. Practicing writing, reading extensively, and using grammar-checking tools will help you identify and correct mistakes. With time, practice, and patience, you’ll be able to improve your grammar skills and become a more confident writer.

Common Grammar Error FAQs

1. How do I know if a sentence is grammatically incorrect?

The subject and verb must both be singular or plural to make a sentence grammatically correct. In other words, the subject and verb must agree. Check for this after writing sentences.

2. What are some common grammar mistakes in academic writing?

Comma splices as well as dangling and misplaced modifiers are common errors in academic writing. The academic world also tends to frown upon contractions in writing (they’re, it’s, can’t, etc.), as they’re considered informal.

3. How do I fix common grammar mistakes in my writing?

After you’ve finished writing your paper, we recommend proofreading it to catch common errors. If you’re uncomfortable doing this yourself, we suggest leaving it up to our team of experts! We’ll check your work for common grammar mistakes, ensure perfect spelling, and much more. Consider submitting a 500-word document for free today!

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