The Most Common Grammar Mistakes (and How to Fix Them)

Chelsea Seegmiller
Feb 25
2 min read

With eight years of editing experience, I've encountered a wide range of grammar mistakes. Below are some of the most common mistakes and simple ways to fix them!

1. Its vs. It’s

The mistake: Many writers confuse "its" (possessive) with "it’s" (a contraction for "it is" or "it has").

Fix it: If you can replace the word with "it is" or "it has," use "it’s." Otherwise, use "its."

Correct: The dog wagged its tail.
Correct: It’s going to rain today.

2. Your vs. You’re

The mistake: "Your" is possessive, while "you’re" is a contraction for "you are."

Fix it: Read the sentence aloud and replace "you’re" with "you are." If it doesn’t make sense, "your" is the correct choice.

Correct: Your book is on the table.
Correct: You’re going to love this movie.

3. There, Their, and They’re

The mistake: These homophones are commonly misused.

Fix it:

"There" refers to a place or introduces a sentence (e.g., There is a cat on the porch).
"Their" shows possession (e.g., Their car is red).
"They’re" is a contraction for "they are" (e.g., They’re going to the concert).

4. Affect vs. Effect

The mistake: "Affect" is usually a verb, while "effect" is usually a noun.

Fix it: Use "affect" when describing an action and "effect" when referring to a result.

Correct: The weather will affect our travel plans.
Correct: The new law had a positive effect on the economy.

5. Misplaced Apostrophes

The mistake: Apostrophes are often used incorrectly in plurals and possessives.

Fix it:

Use an apostrophe to show possession (e.g., Sarah’s book).
Do not use an apostrophe for plurals (e.g., The Smiths, not The Smith’s).
For plural possession, place the apostrophe after the "s" (e.g., The dogs’ owner was kind).

6. Comma Splices

The mistake: A comma splice occurs when two independent clauses are joined with just a comma.

Fix it: Use a period, semicolon, or conjunction instead.

Incorrect: I love to write, it's my passion.
Correct: I love to write. It's my passion.
Correct: I love to write; it's my passion.
Correct: I love to write, and it's my passion.

7. Run-on Sentences

The mistake: Run-on sentences combine multiple independent clauses without proper punctuation.

Fix it: Break the sentence into smaller ones or use proper punctuation.

Incorrect: She loves coffee she drinks it every morning.
Correct: She loves coffee. She drinks it every morning.

8. Who vs. Whom

The mistake: Many people use "who" when "whom" is correct.

Fix it: Use "who" as the subject of a sentence and "whom" as the object. If you can replace it with "he/she," use "who." If you can replace it with "him/her," use "whom."

Correct: Who is coming to the party? (He is coming.)
Correct: To whom should I address the letter? (I should address it to him.)