English grammar mistakes happen to everyone—students, professionals, native speakers, and English learners alike. English contains many rules, exceptions, and confusing word pairs, which makes errors common even for advanced writers.
As an English writing instructor working with ESL students, I’ve noticed that most learners repeat the same grammar mistakes. After reviewing hundreds of essays and assignments, these 30 errors appear more than any others.
The good news is that you don’t need to memorize every grammar rule to improve your English. By understanding the most common grammar errors and learning how to correct them, you can quickly make your writing clearer, more confident, and more professional.
In this guide, you’ll learn:
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The 30 most common grammar mistakes in English
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Incorrect vs correct sentence examples
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Simple grammar rules explained clearly
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Practical tips you can remember easily
Common Grammar Errors
Quick Cheat Sheet: Most Common Grammar Errors
If you’re short on time, these mistakes appear most often:
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Subject–verb agreement errors
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Comma splices and run-on sentences
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Your vs you’re
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Its vs it’s
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Their vs there vs they’re
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Fewer vs less
Each one is explained below with examples.
Common Grammar Errors Explained
1. Subject–Verb Agreement Error
Incorrect sentence:
The list of items are on the table.
Correct sentence:
The list of items is on the table.
Grammar rule:
The verb must agree with the main subject, not nearby words.
Explanation:
The subject is list, which is singular, so the verb must also be singular.
2. Pronoun–Antecedent Agreement Error
Incorrect sentence:
Every student must bring their book.
Correct sentence:
All students must bring their books.
Grammar rule:
Pronouns must match the number of the noun they replace.
3. Comma Splice
Incorrect sentence:
I studied hard, I passed the exam.
Correct sentence:
I studied hard, so I passed the exam.
Grammar rule:
Two complete sentences cannot be joined with only a comma.
4. Run-On Sentence
Incorrect sentence:
She loves coffee she drinks it every day.
Correct sentence:
She loves coffee. She drinks it every day.
Grammar rule:
Each independent idea needs proper punctuation.
5. Sentence Fragment
Incorrect sentence:
Because I was tired.
Correct sentence:
I went to bed early because I was tired.
Grammar rule:
A sentence must express a complete thought.
Learning Pattern Tip
Many grammar mistakes happen because English relies on sentence structure and agreement, not just vocabulary. Paying attention to subjects, verbs, and punctuation solves many problems at once.
6. Misplaced Modifier
Incorrect:
She almost drove her kids to school every day.
Correct:
She drove her kids to school almost every day.
Rule:
Place modifiers near the word they describe.
7. Dangling Modifier
Incorrect:
Walking to the store, the rain started.
Correct:
While I was walking to the store, it started raining.
Rule:
The subject performing the action must be clear.
8. Your vs You’re
Incorrect:
Your going to love this movie.
Correct:
You’re going to love this movie.
Rule:
- Your = possession
- You’re = you are
9. Its vs It’s
Correct usage:
The cat cleaned its paws.
Rule:
- It’s = it is
- Its = possessive form
10. Their vs There vs They’re
Correct sentence:
They’re going to the party tonight.
Rule:
- Their = possession
- There = place
- They’re = they are
11. Then vs Than
Incorrect:
She is taller then her sister.
Correct:
She is taller than her sister.
Rule:
Than compares; then refers to time.
12. Affect vs Effect
Correct:
This decision will affect my future.
Rule:
Affect = verb
Effect = noun (result)
13. Fewer vs Less
Correct:
There are fewer students today.
Rule:
Fewer = countable nouns
Less = uncountable nouns
14. Me vs I
Correct:
He and I went to the store.
Tip:
Remove the other person to test the sentence.
15. Who vs Whom
Correct:
Who is calling?
Rule:
Who = subject
Whom = object
Grammar Insight
Most pronoun errors happen because spoken English sounds natural even when grammar is incorrect. Writing requires more precise structure.
16. Incorrect Apostrophes for Plurals
Incorrect:
Apple’s for sale
Correct:
Apples for sale
Rule:
Apostrophes show possession, not plurals.
17. Missing Apostrophes in Contractions
Correct:
I don’t know why she can’t come.
18. Possessive Apostrophes
Teacher’s lounge = one teacher
Teachers’ lounge = many teachers
19. Inconsistent Verb Tense
Incorrect:
She walked into the room and is sitting down.
Correct:
She walked into the room and sat down.
20. Irregular Verb Forms
go → went → gone
write → wrote → written
21. Lay vs Lie
Lie = to rest
Lay = to place something
22. Double Negatives
Incorrect:
I don’t have no money.
Correct:
I don’t have any money.
23. Comparative Errors
Incorrect:
More better
Correct:
Better
24. Parallel Structure
Correct:
She likes reading, swimming, and biking.
25. Article Mistakes (A, An, The)
Correct:
A university student
(Articles depend on sound, not spelling.)
26. Preposition Errors
Correct combinations:
- Married to
- Depend on
27. Which vs That
That = essential information
Which = extra information (with commas)
28. Capitalization Errors
Always capitalize:
- I
- Names and places
- Countries and months
29. Overusing Passive Voice
Passive: Mistakes were made.
Active: We made mistakes.
Active voice is usually clearer.
30. Confusing Similar Words
Borrow = receive
Lend = give
Common Grammar Errors
Practice: Test Your Grammar Skills
Try correcting these sentences:
- Your going to enjoy this lesson.
- There is less mistakes now.
- Him and me went to the meeting.
- She didn’t do nothing wrong.
- The dog wagged it’s tail.
Answers
- You’re going to enjoy this lesson.
- There are fewer mistakes now.
- He and I went to the meeting.
- She didn’t do anything wrong.
- The dog wagged its tail.
FAQs About Common Grammar Errors
What grammar mistakes happen most often?
Subject–verb disagreement, punctuation errors, homophone confusion, and apostrophe misuse.
How can I improve grammar quickly?
Practice correcting real sentences instead of memorizing rules.
Why are “your” and “you’re” confusing?
They sound identical but serve different grammatical functions.
Conclusion: How to Avoid Grammar Errors
Grammar becomes easier when you focus on patterns instead of memorizing rules. These 30 common grammar mistakes appear repeatedly in everyday English writing. By recognizing them and practicing corrections regularly, you can significantly improve clarity and confidence in communication.
Start small. Fix one mistake at a time, review examples often, and apply the rules in real writing situations. Clear grammar leads to clear communication.