Common Grammar Mistakes and How to Avoid Them

Clear and accurate writing depends on proper grammar. Mistakes in punctuation, sentence structure, or word choice can confuse readers and weaken your message.

Whether you are a native speaker or learning English, strong grammar skills help you communicate more effectively.

For many English learners, choosing the right words in different contexts is a common challenge.

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As a global language, English is essential in both personal and professional settings, but its complex rules and exceptions can make it difficult to master. Even skilled writers face grammar hurdles.

In this blog, we will explore common grammar mistakes and provide simple ways to fix them. With a few key strategies, you can improve your writing, boost clarity, and express your ideas with confidence. 

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Top 15 Common English Grammar Mistakes and Tips to Avoid Them

Below is a list of 15 frequent grammar mistakes with tips on how to fix them.

1. Confusing Present and Past Tenses

Many people struggle with verb tenses, especially when discussing past events. The simple past tense is used for actions that happened and finished in the past, while the present perfect is used for actions that still have relevance to the present. 

For example, "When I was young, I have lived in New York" is incorrect because "have lived" suggests an ongoing action. 

The correct sentence is "When I was young, I lived in New York." To avoid this mistake, always determine whether an action is completely in the past or has a connection to the present before choosing the verb tense.

2. Overusing Adverbs

Adverbs are useful in writing, but overusing them can make sentences weak and repetitive. Instead of relying on adverbs, try using stronger verbs. 

For instance, instead of saying, “She really quickly ran to the door,” you can say, “She dashed to the door.”

The word dashed already conveys both speed and intensity, making the adverb quickly unnecessary. 

Overusing adverbs, especially in formal writing, can make your work sound less polished. To improve clarity, look for ways to replace adverbs with more precise verbs that make your writing more engaging and effective.

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3. Misplacing Apostrophes

Apostrophes are commonly misused, especially when showing possession or contractions. A frequent mistake is using "it's" instead of "its". 

For example, "The cat licked it's tail" is incorrect because "it's" means "it is." The correct sentence is "The cat licked its tail," where "its" is a possessive pronoun. 

Similarly, people often put apostrophes in plurals, such as "apple's" instead of "apples." To avoid this mistake, remember that apostrophes indicate contractions (can’t, don’t, it’s) or possession (John’s book, the dog’s toy), but never plurals.

4. Confusing Your and You’re

The words your and you’re are often misused because they sound the same but have different meanings. Your is a possessive adjective, as in “This is your phone.” 

On the other hand, you’re is a contraction of “you are.” Saying “Your going to be late” is incorrect; the correct form is “You’re going to be late.” 

A simple way to avoid this mistake is to replace you’re with you are—if the sentence still makes sense, you’re using the right word. Paying attention to this distinction will make your writing clearer and more professional.

5. Misusing There, Their, and They’re

These three words are homophones, meaning they sound the same but have different meanings. There refers to a place (“Put the book over there”), their shows possession (“That is their house”), and they’re is a contraction of “they are” (“They’re coming to the party”). 

A common mistake is saying “Their going to the park” instead of “They’re going to the park.” To avoid confusion, try replacing they’re with they are.

if the sentence still makes sense, you’re using the correct word. Taking a moment to double-check will prevent this common grammar error.

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6. Subject-Verb Agreement Errors

The subject and verb in a sentence must always agree in number. A common mistake occurs when people use a plural verb with a singular subject. 

For example, “The list of items are on the table” is incorrect because list is singular, even though items is plural. The correct sentence is “The list of items is on the table.” 

The key to avoiding this mistake is identifying the main subject of the sentence and ensuring that the verb matches it in number.

This rule is particularly important in complex sentences where the subject and verb are separated by other words.

7. Run-On Sentences and Comma Splices

A run-on sentence occurs when two independent clauses are joined without proper punctuation. 

For example, “I went to the store, I bought milk” is incorrect because the comma alone is not strong enough to separate two complete sentences. 

To fix this, you can add a conjunction (“I went to the store, and I bought milk”), use a semicolon (“I went to the store; I bought milk”), or separate them into two sentences. 

Avoiding run-on sentences makes writing clearer and easier to read. Always check if your sentence contains two complete thoughts, and use the appropriate punctuation.

8. Using “Who” and “Whom” Incorrectly

The words who and whom are often confused because they serve different grammatical roles. Who functions as a subject pronoun, meaning it refers to the person performing an action. 

For example, in “Who is knocking on the door?”, who is the subject of the verb is knocking.

On the other hand, whom is an object pronoun, used when referring to the person receiving an action. In “Whom did you invite to the party?”, whom is the object of the verb invite.

A simple trick to determine the correct usage is to replace who or whom with he or him. If he fits, use who; if him fits, use whom. 

For example, in the question “Who/Whom should I call?”, replacing it with I should call him shows that whom is the correct choice. Using this method will help ensure proper grammar in both writing and speech.

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9. Misplacing Modifiers

A misplaced modifier is a word or phrase that is placed incorrectly in a sentence, making the meaning unclear. 

For example, “She only eats vegetables on Mondays” suggests that she does not eat them on other days, when the intended meaning is that she eats only vegetables (not meat) on Mondays. 

The correct sentence is “She eats only vegetables on Mondays.” Always place modifiers as close as possible to the words they describe. Misplacing them can create confusion or unintended meanings, making your writing unclear.

10. Using Double Negatives

A double negative occurs when two negative words are used in the same sentence, canceling each other out and creating confusion. 

For example, “I don’t need no help” technically means “I need help,” which is the opposite of what the speaker intended. The correct sentence is “I don’t need any help.”

In standard English, using a single negative is preferred. While double negatives are sometimes used in casual speech, they should be avoided in writing to maintain clarity and grammatical correctness.

11. Incorrect use of "Its" and "It’s"

A common mistake in writing is confusing its and it’s. Its is a possessive pronoun, while it’s is a contraction of it is or it has.

The mistake often occurs when people assume that all possessive nouns require an apostrophe. 

For example, “The dog wagged it’s tail” is incorrect because it’s means it is. The correct sentence is “The dog wagged its tail.” To avoid this mistake, remember that it’s is only used when you can replace it with it is or it has. If you can’t, then use its.

12. Confusing "Affect" and "Effect"

The words affect and effect are often confused because they sound similar but have different meanings. Affect is usually a verb, meaning to influence something (“The weather affects my mood”), while effect is usually a noun, referring to a result (“The new rule had a positive effect”). 

A common mistake is saying “The medicine had no affect on me” instead of “The medicine had no effect on me.” To avoid this, remember that affect is an action and effect is the outcome of that action. If you are unsure, try replacing the word with result—if it makes sense, use effect.

13. Mixing Up "Than" and "Then"

People often misuse than and then, even though they have distinct meanings. Than is used for comparisons (“She is taller than me”), while then is used to indicate time or sequence (“We went to the store, then we went home”). 

A common mistake is writing “I am better then him” instead of “I am better than him.” To avoid this, remember that than is used when comparing things, whereas then is used when discussing events in order. Reading your sentence aloud can help you identify which word fits best.

14. Using “Me” Instead of “I” (or Vice Versa)

Many people struggle with whether to use I or me in a sentence, especially when talking about more than one person. For example, “Me and my friend went to the store” is incorrect because me is an object pronoun, but here it’s used as a subject. 

The correct sentence is “My friend and I went to the store.” A simple trick to avoid this mistake is to remove the other person’s name and check if the sentence still makes sense. You wouldn’t say “Me went to the store”, so you shouldn’t say “Me and my friend went to the store” either.

15. Confusing “Who” and “Whom”

The difference between who and whom confuses many people. Who is a subject pronoun, while whom is an object pronoun. A common mistake is writing “Whom is calling?” instead of “Who is calling?” because who is the subject of the sentence. 

However, in a sentence like “To whom should I give this?”, whom is correct because it is receiving the action. A useful trick is to replace who/whom with he/him—if he fits, use who; if him fits, use whom. For example, “Who/whom should I invite?” → “I should invite him” (so whom is correct).

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