Even experienced writers make grammar mistakes. Some errors are subtle enough to slip past a quick read but obvious enough to damage your credibility with readers or editors. Below are the 10 most common grammar mistakes — and exactly how to fix them.
1. Your vs. You're
Your is a possessive pronoun (your book, your idea). You're is a contraction of "you are."
❌ Your going to love this.
✅ You're going to love this.
2. Its vs. It's
Its is possessive (the dog wagged its tail). It's means "it is" or "it has."
❌ It's color is red.
✅ Its color is red.
3. There, Their, and They're
- There refers to a place or idea: "The book is over there."
- Their is possessive: "Their report was excellent."
- They're = they are: "They're working late."
4. Subject-Verb Disagreement
Subjects and verbs must agree in number. Singular subjects take singular verbs; plural subjects take plural verbs.
❌ The team are winning.
✅ The team is winning.
Tricky cases include collective nouns (team, committee, group), which are typically treated as singular in American English.
5. Misplaced Apostrophes
Apostrophes show possession or mark contractions. They are never used to make a word plural.
❌ The 1990's were great.
✅ The 1990s were great.
❌ Three cat's sat on the mat.
✅ Three cats sat on the mat.
6. Dangling Modifiers
A dangling modifier is a phrase that doesn't logically connect to the word it's meant to describe.
❌ Running down the street, the car hit a pothole. (Cars don't run.)
✅ Running down the street, I noticed the car hit a pothole.
7. Comma Splices
A comma splice joins two independent clauses with only a comma. Fix it with a period, semicolon, or a coordinating conjunction (and, but, so).
❌ She finished the report, she sent it to the client.
✅ She finished the report and sent it to the client.
8. Who vs. Whom
Use who as a subject, whom as an object. A quick test: if you can answer with "him/her," use "whom."
❌ Who did you send the email to?
✅ Whom did you send the email to? (You sent the email to him.)
9. Using "I" and "Me" Incorrectly
Remove the other person from the sentence to test which pronoun is correct.
❌ Between you and I, this is wrong.
✅ Between you and me, this is right. (Would you say "between I"? No.)
10. Passive Voice Overuse
Passive voice isn't always wrong, but overusing it makes writing weak and wordy.
❌ The report was written by the team. (passive)
✅ The team wrote the report. (active)
How an AI Grammar Checker Helps
Catching these errors manually takes time, especially in long documents. Our AI Grammar Checker scans your text for all of the above mistakes and more — with clear explanations so you understand why something is wrong, not just that it is.
After fixing grammar, consider running your text through the Paraphraser to improve flow, or the Humanizer if you used AI to draft your content.
FAQ
What's the most common grammar mistake?
Subject-verb disagreement and apostrophe misuse are consistently among the most frequent, even in professional writing.
Does grammar matter in informal writing?
In casual emails or social media, minor errors are often overlooked. But in professional, academic, or published writing, grammar errors hurt credibility significantly.
Can AI fix all grammar mistakes?
AI grammar checkers catch the vast majority of standard errors but can occasionally miss subtle stylistic issues or context-dependent nuances. Always do a final human review.