30 Common Grammar Mistakes and How to Avoid Them

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Candace Osmond

Candace Osmond studied Advanced Writing & Editing Essentials at MHC. She’s been an International and USA TODAY Bestselling Author for over a decade. And she’s worked as an Editor for several mid-sized publications. Candace has a keen eye for content editing and a high degree of expertise in Fiction.

Even the best writers have made grammatical mistakes in their work. Heck, even the creators of grammar rules probably committed the same errors!

English grammar rules can be confusing, so I created a list of the thirty common grammar mistakes you should avoid with examples. Consult this list when you’re self-editing to sound like a native speaker in your next writing. 

Is a Typo a Grammatical Error?

A grammatical error is a mistake based on prescriptive grammar that shows unconventional or faulty usage. Some examples include a misplaced modifier or dangling modifiers.

Typographical errors are not grammatical errors because they do not show unconventional usage of English words. Instead, they are unintentional mistakes that occur when you accidentally type the wrong letter, number, or symbol on the keyboard.

You can correct typographical errors without consulting the rules of grammar. Proofreading is one way to avoid these inconsistencies. 

How Do You Avoid Grammar Mistakes?

An online writing editor like Grammarly will help you catch your overlooked grammar mistakes. These online writing assistants can also check for spelling mistakes, unclear sentences, and inappropriate tone in your documents. You can learn more about Grammarly’s accuracy and reliability here.

But the best way to avoid grammar mistakes is by learning the basic grammar rules and following them. No amount of online grammar checkers will be able to polish your writing. Take online grammar classes to enhance your sentence structure and word choices. 

Mastering the grammar rules also saves you money from hiring a proofreader for your work. You’ll independently analyze and improve your text without needing anyone’s assistance.

30 of the Most Common Grammatical Errors

Here’s a look at the 30 most common grammatical mistakes you should avoid if you want to sound more intelligent. 

They’re vs. Their vs. There

The most common grammar mistake you should avoid is getting confused between “they’re,” “their,” and “there.” Committing this error is understandable because these words are homophones or words with the same pronunciation.

The first one is a contraction for “they are.” 

Example: They’re heading to the store.

“Their” is a possessive pronoun you should use when referring to an object owned by a group. 

Example: They’re heading to the store with their husbands.

“There” refers to a place you’re pointing. 

Example: Their husbands are waiting over there

Avoid this common mistake by always double-checking your sentences.

Your vs. You’re

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“Your” and “you’re” are another pair of words with identical sounds but different spellings and meanings. The difference between these two terms is that one takes ownership while the other is being. 

The first word, “your,” is a possessive pronoun.

Example: Your new haircut looks good on you.

“You’re” is a contraction of “you are.”

Example: You’re driving too fast.

If you’re having difficulty memorizing the two, consult advanced grammar checkers like Grammarly.  

Its vs. It’s

Even the best writers get confused about this grammatical mistake. “Its” may seem like an ambiguous pronoun, but it shows an animal, event, or object taking ownership of something. 

Example: This sandwich is past its expiration day.

Meanwhile, “it’s” with an apostrophe is a contraction of “it is.” 

Example: It’s a beautiful day to be happy. 

The key to remembering these grammar rules is to note that words with apostrophes are shortened versions of two words. It also applies to “you’re” and “they’re.”

Incomplete Comparisons

Only a few people know about this common grammar error. Can you see what’s wrong with this sentence?

Jillian looks happier and more motivated.

There are two modifiers in the comparative degrees. The first is “happier,” while the other is “more motivated.” But what makes it wrong is the lack of a noun to whom you’re comparing Jillian. Happier than who? More motivated than what?

Always be clear with the nouns you’re comparing. Otherwise, your readers will be frustrated with your text. Here’s a better example.

Jillian looks happier and more motivated than she was five months ago.

While the writer did not compare Jillian to anyone else, they compared her to her past self. 

Passive Voice

Using the passive voice is not necessarily a grammatical mistake, but overuse of this sentence shows bad grammar. 

Passive sentences occur when the object of the sentence starts the sentence instead of appearing at the end. The result is a weak, dull, and unclear piece of writing that doesn’t have a subject.

Any experienced writer knows the importance and benefits of active writing. Active voice construction makes you sound more engaging and professional.

A basic rule of thumb is to ensure every sentence in your paragraph is active. The only times you can use the passive voice is when it’s essential to highlight the action instead of who’s doing it.


  • The car was driven by her son (passive).
  • Her son drove the car (active).

You can use an advanced grammar checker to correct passive sentences in your text.

Dangling Modifiers

Dangling modifiers are one of the many pet peeves of editors. It’s a word, modifier, or phrase that describes a word in a sentence that is not clearly defined. 

Example: Sick of all the games, their relationship finally came to an end.

Who is sick of all the games? One might assume that the “relationship” is sick of all the games because it’s the closest noun to the modifier. Here’s the correct sentence.

Sick of all the games, Mary decided to end the relationship. 

“Mary” is being modified by the modifier “sick of all the games.”

It’s also much better to flip the sentence structure around. 

Mary decided to end the relationship because she was sick of all the games. 

Referring to a Brand or Entity as ‘They’

Calling a business or brand “they” is a sign of a bad writing habit. Although it makes sense because a company is made of several people, an entity in itself is still singular. 

“He” or “she” sounds wrong when the antecedent is genderless. Use “it” instead.

Example: FedEx reports a decline in its profit due to labor shortages.

It might seem strange to refer to FedEx as “it” or “its,” but it will sound more natural once you’re used to it. 

Possessive Nouns

Possessive nouns typically include an apostrophe and an S. But where should you put the apostrophe?


  • Most of the student’s papers are missing.
  • Most of the students’ papers are missing.

Both statements are correct but have different meanings. In the first sentence, the apostrophe is placed before the S. It implies that there is only one student whose papers are missing. The second sentence means many students have missing papers. 

Here are the general rules for using possessive nouns to avoid poor grammar:

  • Add an apostrophe following the letter S if the noun is plural.
  • Place an apostrophe before the S for a singular noun.
  • Add an apostrophe after the S if you have a singular noun that ends with an S.

More Common Grammar Mistakes

Overusing Adverbs

The overuse of adverbs is one of many grammar errors you should avoid in your writing. It’s a word that modifies a verb, adjective, or a fellow adverb. You should avoid using too many adverbs, no matter how useful they are. However, completely avoiding adverbs is not recommended in formal documents, including business and academic writing.

Avoiding adverbs is not recommended in formal documents, including business and academic writing. It makes the writer look lazy and messy, especially when using filler adverbs and “-ly” adverbs.

Here are some filler adverbs to avoid:

  • Really.
  • Highly.
  • Surely.
  • Totally.
  • Simply.
  • Most.
  • Just.
  • Slightly.

Misplacing Apostrophes

I’ve already mentioned misplacing apostrophes in possessive nouns. But there are other ways you can misplace this punctuation. 

Remember that apostrophes indicate ownership or contracted words. 


  • Can’t = Cannot.
  • Shouldn’t = Shouldn’t.

Always place the apostrophe where the missing letters of the contraction are. For example, it should be “can’t” instead of “ca’nt” because the missing O in “cannot” is between the N and T.

Another rule to note is that you should never use apostrophes to make a word plural.

Two vs. Too. vs. To

These three words sound the same but should be used in different contexts. “Two” is a number that comes after one.

Example: I accidentally paid two times. 

“Too” shows a higher degree or an alternative to “in addition.”


  • I’m too scared to try that ride.
  • Is he joining us too?

“To” is a preposition that indicates direction, contact, or purpose. You are likely to find this word before an infinitive verb.


  • I’m going to her house this Monday.
  • Apply some polish to the wooden furnishings.
  • I want to purchase a dress for my graduation.

Here vs. Hear

“Here” and “hear” are also among the most classic grammar mistakes you might commit. The first word is a modifier that points somewhere close. It means “in, on, or at this location.”

Example: I’m here inside the mall.

“Hear” is a verb meaning the act of perceiving sounds using one’s ear. 

Example: I can’t hear your voice without the microphone. 

Confusing Adjectives and Adverbs

The difference between adverbs and adjectives is often confusing and can result in a poor writing style. Your text will sound uneducated and informal to your readers. 


  • Incorrect: Thanks for the real good meal.
  • Correct: Thanks for the really good meal.
  • Better: Thanks for the good meal.

“Real” is an adjective. But you need to use its adverb form because you’re modifying the adjective “good” and not the noun “meal.”

However, “really” is a filler adverb, so it’s best to remove it altogether. 

Here’s another example:

  • Incorrect: She rushed quick inside the room when the bell rang.
  • Correct: She rushed quickly inside the room when the bell rang.

Pronoun Disagreement

Sometimes, you think you have the perfect grammar until you find out you’re using the wrong pronouns. Always check if your nouns and pronouns agree with each other, as not all grammar-checking platforms detect these mistakes.

Remember that singular pronouns always use singular nouns. Plural pronouns, on the other hand, go with plural nouns.


  • Incorrect: Each girl must greet everyone when he comes in.
  • Correct: Each girl must greet everyone when she comes in.

If the antecedent is vague or gender-neutral, you can use “they.” It’s now acceptable to use this plural pronoun even if the noun you’re referring to is singular.

Example: Each person must greet everyone when they come in.

You can also use “he or she,” but it might not show inclusivity to people in the middle of the gender spectrum. 

Comma Splice and Run-On Sentence

Run-on sentences combine two independent sentences or clauses without the proper conjunction or punctuation. The result is a compound sentence with an improper structure.

A comma splice is like a run-on sentence, except you’re using a comma to mix two clauses without a conjunction.

Here’s an example of an incorrect sentence structure:

Timmy is a kind little boy, he assisted the old lady when crossing the street.

There are many ways to fix this statement. First, you can separate them into two sentences.

Timmy is a kind little boy. He assisted the old lady when crossing the street.

Also, you can try replacing the comma with a semicolon. However, many style guides do not recommend using this proper punctuation to join two independent clauses.

Timmy is a kind little boy; he assisted the old lady when crossing the street.

Another solution is to add a coordinating conjunction after the comma. The coordinating conjunctions include “for,” “and,” “nor,” “but,” “or,” “yet,” and “so.”

Timmy is a kind little boy, for he assisted the old lady when crossing the street.

If you want to eliminate the comma, replace it with a subordinating conjunction.

Timmy is a kind little boy because he assisted the old lady when crossing the street. 

Lack of Subject-Verb Agreement

Many grammatical errors are caused by subject-verb disagreement. This oversight happens when you use an incorrect verb tense or auxiliary verb in your sentence. 

Your subjects and verb should agree with one another in number too. If the subject is singular, then so should your verb be. 


  • Incorrect: The men is going to the basketball court.
  • Correct: The men are going to the basketball court.

Sentence Fragments

A sentence fragment is a statement that doesn’t have a complete subject or verb. It often occurs after the writer writes a related idea.


  • Incorrect: Looking forward to working with you.
  • Correct: I’m looking forward to working with you.

Many English writers fail to notice the fragments in their paragraphs because our incomplete thoughts may seem complete on their own. They think it’s enough to express an idea starting with a capital letter and ending with punctuation.

Here’s another example of an incomplete sentence and a complete sentence:

  • Incorrect: Because of him
  • Correct: Because of him, Kesha dyed her hair black.

Missing Comma in Compound Sentence

A compound sentence shows complete and connected thoughts and should always include a conjunction.

Aside from the conjunction, your compound sentence should always have a comma to separate the two ideas. 


  • Incorrect: Megan is at school and Jane went with her.
  • Correct: Megan is at school, and Jane went with her.

You can also separate two sentences into two to avoid overloaded sentences.

No Clear Antecedent

An antecedent refers to a word that comes before or after a pronoun. It allows your audience to understand which word the pronoun is replacing.


  • Incorrect: This is so exciting.
  • Correct: This party is so exciting.

The pronoun “this” should have an antecedent after it. Otherwise, your readers would have no idea what you’re talking about

Sometimes, your antecedent is part of the sentence but still lacks clarity. You can avoid confusion by fixing your sentence structure.


  • Incorrect: Jonah’s father adopted the dog, and he was happy.
  • Correct: Jonah’s father was happy when he adopted the dog.

Ending a Sentence in a Preposition

I bet this grammar rule is something you’ve never heard of. Never end your sentence with prepositions. Take the first sentence of this paragraph as an example. Here’s how you can correct it:

I bet you’ve never heard of this grammar rule.

Ending your statements with prepositions shows unprofessionalism and informalism. It’s only acceptable in casual conversations and friendly types of writing.

Affect vs. Effect

The confusion between the words “affect” and “effect” isn’t a matter of misspelling as much as an error in your choice of words. Both words have very similar meanings and pronunciations, yet they are of different parts of speech.

“Affect” is a verb that means “to create a shift in or act on.” 

Example: The UV rays affect the color of these sneakers.

“Effect” is a noun that refers to “result or consequence.”

Example: The changing color of these sneakers is the effect of the UV rays.

One trick to remember the difference is the acronym RAVEN.

R = Remember

A = Affect is a 

V = Verb

E = Effect is a

N = Noun.

Well vs. Good

Another common grammatical error you should be aware of is mixing up “good” and well.” Both have the same meaning, but “well” is an adverb and “good” is an adjective.

That means “well” should modify a verb, adjective, or a fellow adverb. Below is an example.

She’s doing well in her studies.

“Good” should modify a noun or a pronoun. Take a look at this example.

Bruno is a good dog. 

One exception to this “good” vs. “well” debate is when the verb being modified is “taste.” A certain food should taste good instead of tasting well.

Fewer vs. Less

Some English speakers and writers also mix “less” and “fewer.” To remember the difference them just decide if the item is all one thing or a group of several ones. Use “fewer” for a group of many objects, and use “less” if it’s singular.


  • Incorrect: There’s fewer ice cream in the tub
  • Correct: There’s less ice cream in the tub.

Title Capitalization

Another grammar problem you should resolve in your writing is how you capitalize your titles and headings. The rule of thumb is always to capitalize the first and last words. You should also capitalize every verb, pronoun, and adjective in the title.

Longer conjunctions also require capitalization, along with long prepositions and adverbs.

Example: What I Learned About My Trip to Madrid 


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Inflated sentences are characterized by wordiness because of the unnecessary fillers you’re using. Make your sentence as concise as possible so that readers will understand what you say. You don’t want them to be annoyed by your pointless words.

Make sure you’re using stronger verbs and nouns, so you don’t need to add “very,” “just,” and “really.” 


  • Incorrect: It’s come to my attention that your payment for the rent is overdue, and I urge you to settle your payment as soon as possible.
  • Correct: Your rent is overdue. Please settle your payment now.

Sure, the first statement sounds more polite. But it wastes a few seconds of your recipient’s time. 

Too Many Prepositional Phrases

Most complete sentences contain prepositional phrases. However, excessive use makes your text wordier. Focus on simplifying your statements.


  • Incorrect: I went over to their house.
  • Correct: I visited their house. 

“To their house” is a correct phrase. But it’s better to find a shorter way to say it.


Tautologies are phrases or expressions that say the same idea twice, making your writing longer and undesirable. English experts would also argue that tautologies make you sound foolish. 

Example: I want to see him personally.

The word “personally” repeats the idea of seeing someone. It doesn’t add new information, so it’s best to cut it.

Wrong Comma Usage

You already know that two independent clauses without punctuation indicate bad grammar. But there are other ways you can misuse a comma.

Some people forget to use a comma in a series of elements before the word “and.”


  • Incorrect: red, orange, blue and green.
  • Correct: red, orange, blue, and green.

Always use a comma to separate introductory words and direct address. 


  • At first, I thought you were rude.
  • Tania, you should audition. 

Then vs. Than

“Then” is an adverb which means “at that time” or “after that.” “Than” is a word that shows a comparison. 


  • She tied a string to her brother’s loose tooth and then pulled it hard.
  • You’re taller than me. 

Further vs. Farther

Many people use “further” and “farther” interchangeably. But, there’s actually a big difference between the two. 

“Farther” refers to physical distance.

Example: I traveled farther from the hills.

“Further” is for figurative distances.

Example: The business is falling further away from its aims.  

Set Yourself Up for Writing Success

Whether you’re a business owner, student, or blogger, correct grammar is the hallmark of precise and professional communication. 

You can improve your writing quality through simple corrections like differentiating between fewer and less or practicing subject-verb agreement. Take advantage of the list above to help you avoid common grammatical mistakes.