10 Most Common English Grammar Mistakes ESL Learners Make

English grammar can be tricky, even for advanced learners. After working with thousands of English learners, we have identified the 10 most common grammar mistakes that appear in writing again and again.

The good news? Every one of these mistakes is fixable. In this guide, we will explain each error, show you clear examples, and give you practical strategies to avoid them. Use our free Grammar Checker to practice and catch these mistakes in your own writing.

1. Subject-Verb Agreement Errors

This is the most common grammar mistake English learners make. The subject and verb in a sentence must agree in number — singular subjects need singular verbs, and plural subjects need plural verbs.

The trick is to identify the real subject of your sentence, especially when there are other words between the subject and the verb.

2. Incorrect Article Usage (A, An, The)

Articles are small words but they cause big problems. English has two types of articles: indefinite (a/an) and definite (the).

• Use "a" before consonant sounds: a book, a university (sounds like "yoo")
• Use "an" before vowel sounds: an apple, an hour (silent "h")
• Use "the" when both you and the reader know which thing you are talking about

3. Confusing Your/You're, There/Their/They're, Its/It's

These homophones (words that sound the same but have different meanings) confuse even native speakers.

• Your = belonging to you | You're = you are
• There = a place | Their = belonging to them | They're = they are
• Its = belonging to it | It's = it is

4. Preposition Mistakes (In, On, At, For, Since)

English prepositions are notoriously difficult because they do not always translate directly from other languages. Here is a quick guide:

• At = specific time or place: at 3 PM, at the bus stop
• In = months, years, cities, general areas: in July, in London
• On = days, dates, surfaces: on Monday, on the table
• For = duration: for 3 years
• Since = starting point: since 2020

For a deeper dive, read our full guide on common preposition mistakes English learners make.

5. Double Negatives

In English, using two negatives in the same sentence creates a positive meaning — or just sounds confusing. Avoid using "not" with negative words like "nothing", "nobody", or "never".

6. Misusing "Then" vs "Than"

These two words are often confused in writing:

• Then = next, after that: "First we eat, then we leave."
• Than = comparison: "She is taller than me."

7. Run-On Sentences (Comma Splices)

A run-on sentence happens when you join two complete sentences with just a comma (or nothing at all).

8. Wrong Word Order in Questions

English questions follow a specific structure. Many learners keep the statement word order when asking questions.

For yes/no questions: Auxiliary verb + subject + main verb.

9. Missing or Wrong Prepositions After Verbs

Some English verbs require specific prepositions. Using the wrong one changes the meaning or sounds unnatural.

10. Confusing Adjectives and Adverbs

Adjectives describe nouns; adverbs describe verbs, adjectives, or other adverbs. The most common error is using an adjective where an adverb is needed.

How to Practice and Improve

Knowing the rules is only half the battle. Here is how to actually improve:

1. Write daily — Even 5 minutes of writing helps build good habits.
2. Use our Grammar Checker — Paste your text and see which mistakes you are making.
3. Read your writing aloud — Many errors sound wrong when spoken.
4. Keep a mistake journal — Write down each mistake and the correction.
5. Use the Readability Checker — Short, clear sentences have fewer grammar errors.