common grammar mistakes even smart people make

grammar mistakes happen to everyone. even professional writers make them. the problem is, these errors can make you look careless — especially in emails, resumes, and important documents.

here are the most common mistakes and how to avoid them.

1. your vs. you're

your = possessive (something belongs to you) you're = contraction of "you are"

wrong: "Your going to love this." right: "You're going to love this."

test: replace with "you are." if it works, use "you're."

2. its vs. it's

its = possessive (belonging to it) it's = contraction of "it is"

wrong: "The company changed it's policy." right: "The company changed its policy."

test: replace with "it is." if it works, use "it's."

3. their vs. there vs. they're

their = possessive (belongs to them) there = location they're = contraction of "they are"

wrong: "Their going to there house." right: "They're going to their house."

4. affect vs. effect

affect = verb (to influence) effect = noun (the result)

wrong: "The weather will effect our plans." right: "The weather will affect our plans."

memory trick: Affect is the Action, Effect is the End result.

5. comma splices

a comma splice joins two complete sentences with just a comma. that's wrong.

wrong: "I love coffee, it keeps me awake." right: "I love coffee. It keeps me awake." also right: "I love coffee; it keeps me awake." also right: "I love coffee because it keeps me awake."

6. run-on sentences

two complete thoughts smashed together without punctuation.

wrong: "I went to the store I bought milk." right: "I went to the store. I bought milk."

7. subject-verb agreement

singular subjects need singular verbs. plural subjects need plural verbs.

wrong: "The list of items are on the table." right: "The list of items is on the table."

the subject is "list" (singular), not "items."

8. who vs. whom

who = subject (doing the action) whom = object (receiving the action)

test: replace with he/him. "he" = who, "him" = whom.

example: "Who/Whom should I contact?" test: "I should contact him." → whom is correct.

9. fewer vs. less

fewer = countable things less = uncountable things

wrong: "Less people showed up." right: "Fewer people showed up."

wrong: "I have fewer time today." right: "I have less time today."

10. dangling modifiers

the modifier doesn't clearly connect to what it's modifying.

wrong: "Walking to work, the rain started." (the rain wasn't walking to work)

right: "Walking to work, I got caught in the rain."

11. apostrophe abuse

apostrophes show possession or contraction. they don't make plurals.

wrong: "I bought apple's and orange's." right: "I bought apples and oranges."

wrong: "The Smith's live here." right: "The Smiths live here."

12. then vs. than

then = time (next, after that) than = comparison

wrong: "I'm taller then you." right: "I'm taller than you."

13. could of vs. could have

"could of" is never correct. you're hearing "could've" (could have).

wrong: "I could of gone." right: "I could have gone."

same applies to: would have, should have, might have.

14. loose vs. lose

loose = not tight lose = to misplace or fail to win

wrong: "Don't loose your keys." right: "Don't lose your keys."

15. incomplete comparisons

wrong: "Our product is better." right: "Our product is better than the competition."

better than what? complete the comparison.

why grammar matters

yes, people will still understand you with grammar mistakes. but:

• errors in professional contexts hurt credibility
• resumes with mistakes get rejected
• unclear writing wastes everyone's time
• consistent errors become habits

you don't need perfect grammar. you need good enough grammar that errors don't distract from your message.

the fix

read your writing aloud. your ear catches what your eye misses. and when in doubt, use a grammar checker to catch what you miss.