31 Common Grammar Mistakes and How To Correct Them

Updated March 10, 2023

Proper grammar is essential when you're creating materials, sharing information, emailing colleagues or submitting a resume or cover letter. Clean and formal writing free from grammar mistakes can help enhance the professionalism of the documents you create. If you're applying for new positions or writing important materials, knowing about common grammatical errors can help you address them quickly and improve your content.

In this article, we list 31 common grammar mistakes and provide examples to help you identify and fix them.

31 common grammar mistakes

Communication is a valued skill in the workforce. Using correct grammar shows attention to detail and effective communication, both skills that are valuable to current and prospective employers. Written communication that is free from grammatical errors in the way you spell words, complete sentences and use punctuation all show how effective you are as a communicator. Here are common grammar mistakes to correct in your writing:

1. Spelling a word wrong

When you type, it's easy to change a word or leave out a letter. When you finish a piece of writing, check your spelling by rereading your work or using a digital tool to help look for errors.


  • Incorrect: I would like a peice of pie.

  • Correct: I would like a piece of pie.

Related: 22 Degrees in Writing

2. Choosing the wrong word

Searching for the right word doesn't always mean you find it. You might choose a word that looks or sounds similar but doesn't have the same definition. For example, the word "loose" means something isn't tight, while "lose" means to misplace something.


  • Incorrect: My coworker said he used a financial planner to help choose his stocks so he wouldn't loose money.

  • Correct: My coworker said he used a financial planner to help choose his stocks so he wouldn't lose money.

3. Unnecessary comma

Commas are used to separate and group ideas. However, you may not need a comma even though there are multiple ideas in a sentence.


  • Incorrect: Sharon and Sue, went into the office early yesterday, to complete a project.

  • Correct: Sharon and Sue went into the office early yesterday to complete a project.

"Sharon and Sue went to the office" is an independent clause (meaning it can stand alone as a sentence), while "to" is a preposition that starts a subordinate clause (meaning a clause that can't stand alone as a sentence but adds more information to an independent clause).

Related: How To Avoid Common Grammar Mistakes in Advertising

4. Commas in a series

When listing a series of things in a sentence, you need to separate the list items by commas. The last item in the list is correct with or without a comma because of the Oxford comma rule. If you choose to use Oxford commas, use them consistently throughout your writing. You can also consult a style guide if applicable to help guide your comma usage.


  • Incorrect: We sold software hardware and computer parts.

  • Correct with an Oxford comma: We sold software, hardware, and computer parts.

  • Correct without an Oxford comma: We sold software, hardware and computer parts.

5. Comma splice

Using a comma to join two independent clauses (sentences) together is a common mistake. If you want to join two independent clauses, you can use a semicolon.


  • Incorrect: I ordered pizza, I also ordered garlic knots.

  • Correct: I ordered pizza; I also ordered garlic knots.

Related: Is It Detail-Oriented or Detailed-Oriented? (Plus Other Common Grammar Errors on Resumes)

6. Introductory commas

Commas are necessary for setting apart an introductory clause. This means that when you start a sentence with a phrase that sets up the rest of the sentence, you need a comma before the sentence continues.


  • Incorrect: If we can't meet I'll call you.

  • Correct: If we can't meet, I'll call you.

Related: How To Write an Article in 7 Easy Steps

7. Missing comma in a compound sentence

You can combine two independent clauses using a comma, but it needs the help of a coordinating conjunction. And, but and or are the most common of the seven coordinating conjunctions. In the correct version of this sentence, the two independent clauses about "Steve" and "Clint" are joined with a comma and the conjunction "and."


  • Incorrect: Steve gave the presentation to the new client and Clint spoke to the board of directors.

  • Correct: Steve gave the presentation to the new client, and Clint spoke to the board of directors.

8. Unclear pronouns

Pronouns take the place of a noun in a sentence. If there are multiple subjects in a sentence, pronoun use can get confusing, so try to ensure it's clear who you're referring to when you use a pronoun. In the following examples, "Bob" and "Pete" both may use "he" as their preferred pronoun, so it could be unclear which one shared pictures based on where you use pronouns. 


  • Incorrect: When Bob and Pete were staying at the convention, he used social media to share pictures.

  • Correct: When Bob and Pete were staying at the convention, Bob used social media to share pictures.

  • Correct: When they were staying at the convention, Bob used social media to share pictures.

Related: The Writing Process: Over 45 Tips on Writing

9. Using quotation marks

When you're sharing someone's exact words, you offset with quotation marks before and after the quote. If your quote ends your sentence, you put the period inside the quote. If not, you can use a comma inside the quote to continue the sentence.


  • Incorrect: At the annual meeting, the CEO told employees this year has been exceptional because of you.

  • Correct: At the annual meeting, the CEO told employees, "This year has been exceptional because of you."

10. Capitalization

You capitalize certain words every time you use them. For example, always capitalize the pronoun "I" and proper nouns, which are names of people, places, historical events, brand names, days of the week, holidays and some titles.


  • Names of people, places and groups/organizations: Aunt Sarah, South America and National Pet Society

  • Titles: Mayor Jensen and Sgt. Rodriguez

  • Historical events and time periods: The American Revolution or The Renaissance

Related: 27 Proofreading Tips That Will Improve Your Resume

11. Missing words

Try to reread your work to ensure you haven't left out small words, like articles and conjunctions that clarify a sentence. To ensure you catch missing words, you may read through sentences backward. You can also read them out loud or ask a friend to look through them because they may be more likely to catch the omission.


  • Incorrect: I bought winning lottery ticket the corner store.

  • Correct: I bought my winning lottery ticket at the corner store.

12. Writing numbers

You generally spell out numbers smaller than 10, though there are exceptions for things like ages or dimensions. For numbers 10 or larger, you typically use the figure, with exceptions for numbers in the millions, billions and trillions. If you're using a certain citation style, try to check for specific rules. When listing numbers, it's important to be consistent with either figures or words.


  • One million listeners

  • 55,600 people

  • 6 eggs, 2 cups of flour and 1 cup of sugar

Related: 5 Ways To Improve Your English Writing Skills

13. Verb tense shift

When you write, try to choose a verb tense to use for the entire document. A common mistake is to change or shift the verb tense in the middle of a piece of writing.


  • Incorrect: I went to the movies with my sister. We will see the new comedy about dancing dogs.

  • Correct: I went to the movies with my sister. We saw the new comedy about dancing dogs.

14. Possession vs. plural

Adding an apostrophe and an "s" to a word shows ownership, but it doesn't make a word plural. In some cases, you might use an apostrophe and an "s" to show ownership.


  • Possession: The computer's processing speed.

  • Plural: The computers are in the office.

Related: 5 Basic Writing Skills and How to Improve and Highlight Them

15. Run-on sentence

You can avoid run-on sentences, which often occur when a writer doesn't join independent clauses properly, by separating multiple ideas into their own sentences or connecting independent clauses using a comma and a conjunction.


  • Incorrect: I wanted to visit the zoo, and I wanted to see the aquarium, and I also wanted to visit the pet rescue center.

  • Correct: I wanted to visit the zoo, see the aquarium and visit the pet rescue center.

  • Correct: I wanted to visit the zoo and the aquarium. I also wanted to visit the pet rescue center.

16. Pronoun agreement

When you write, try to match the correct form of a pronoun (plural or singular) to the subject's preferred pronoun. If you don't know their preferred pronoun, you can use "they" or "their."


  • The boy took his turn on the field.

  • The boys took their turn on the field.

  • Sam took their turn on the field.

17. Hyphens

You most often use hyphens to create a one-word adjective from two words or to combine figures.


  • Tom is a well-known manager.

  • He sells lavender-scented candles.

  • Eighty-five years ago, his life changed.

18. Sentence fragments

Fragments are incomplete clauses that can't stand alone as a sentence. Instead, try using the fragment as a dependent clause you connect to a complete sentence. A complete sentence contains a subject and a predicate.


  • Fragment: Nibbled in the woods.

  • Complete sentence: The deer nibbled on bark in the woods.

19. Subject-verb agreement

When you compose a sentence, the verb must agree with or match the subject. This means if you have a singular subject, you use a singular verb. If you have a plural subject, you use a plural verb.


  • Singular subject: The cat likes its new toy.

  • Plural subject: The cats like their new toy.

Related: FAQ: What Can I Do When My Resume Has a Typo? (With Tips)

20. Misplaced modifiers

To make sure you're describing the right object, try to use an adjective directly before the word you want to modify or describe. This can help you avoid confusion or giving something a quality it doesn't have.


  • Incorrect: He ordered a meal from the restaurant that was high in protein.

  • Correct: He ordered a meal that was high in protein from the restaurant.

21. Lacking parallel structure

Humans often understand things better when they're in patterns. When you write, it's important to use consistent patterns in the structure of your lists and sentences.


  • Incorrect: In college, I studied physics, mathematics, took music lessons and science.

  • Correct: In college, I studied physics, mathematics and science. I also took music lessons.

22. Overly wordy sentences

Sometimes, using a lot of descriptions can be important, but when sentences can become hard to read if they contain more information than is necessary. If you find a long sentence, look for ways to tighten it by eliminating words or breaking your ideas into several sentences.


  • Incorrect: Jake ate a robust meal that tickled his tastebuds and reminded him of the warm, summer days back on at the rustic lake cottage his family of two parents and nine siblings would visit whenever they were able to take a break after school ended for the term. 

  • Correct: Jake's meal reminded him of the summer vacations his family would take to their lake cabin.

23. Semicolon vs. colon

You use a semicolon to combine sentences or long lists, while a colon can take the place of saying "it is" or "they are" to begin a list or state an idea. Using these correctly can improve how easy your writing is to read.


  • Semicolon: Yesterday was my day off; my family went to the beach for a picnic.

  • Colon: My dentist gave me great advice: brush two times every day and floss nightly.

Read more: Semicolon vs. Colon: What’s the Difference? (Plus Examples)

24. Titles of written or created works

These rules may change depending on the style guide you follow, but you generally capitalize all words in a title. Some exceptions to this are articles and prepositions or conjunctions that are of three or fewer letters unless they start or end the title. Common guidelines suggest you put quotation marks around the names of all books, movies, plays, poems, albums, songs, operas, radio and television programs, lectures, speeches and works of art, with a couple of exceptions. These include holy books, reference catalogs, software titles, apps, video games or sculptures.


  • Book: "The Ethics of Sales"

  • Application: Life on the Farm

  • Artwork: "Beautification"

25. Their, there and they're

Many people confuse these words because they sound similar, but they all have distinct meanings. "Their" is a pronoun that shows possession, and "there" indicates a place. "They're" is the contraction they are.


  • Kendall and Colin are going to see if their test results are back.

  • Bryan and Katherine are over there by the tree.

  • They're going to visit Jared and Nicolle this evening.

26. It's and its

It's also common to swap the contraction it is with its, which shows possession. Because an apostrophe normally indicates possession, "its" seems like the opposite of the rule because it doesn't use an apostrophe. 


  • It's a lovely day for a picnic.

  • The milk has exceeded its expiration date.

27. Affect vs. effect

To use these words correctly, remember that "effect" is usually a noun and "affect" usually is a verb. Something can have an effect on you or can affect a change in something.


  • Her speech talked about the positive effects of taking intentional breaks.

  • Her speech affected how I went about my schedule for the rest of the day.

28. "Of" instead of "have"

Sometimes, informal speech can make its way into professional writing. Because of this, people write words incorrectly based on how they sound. One of the most common examples of this is with "of" and "have."


  • Incorrect: I could of won the race if I trained more.

  • Correct: I could have won the race if I trained more.

  • Correct: I could've won the race if I trained more.

29. Who vs. that

When describing a person, use who. When you're describing an object, use that.


  • Wasn't it Amy who went to Rome last year?

  • Rome is the city that Amy visited.

30. Passive voice

Strong writing uses active verbs, meaning the subject does the action and doesn't have the action done to them. Your voice also becomes passive when you put the object of the sentence first.


  • Passive voice: The test was passed by most students.

  • Active voice: Most students passed the test.

Related: How To Become a Proofreader (Characteristics and Tips)

31. Then and than

Another set of similar words people often confuse is "then" and "than. "Use "then" to show what happens next and "than" to make a comparison.


  • I went to the office, then I started my meeting.

  • The meeting lasted longer than my presentation.

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