Common Grammar Mistakes and How to Fix Them

1. Their / They’re / There

✅ Their house is blue.        (possessive)
✅ They're going to the park.  (they are)
✅ The book is over there.     (location)

Test: Replace with “they are.” If it fits, use “they’re.”

2. Its / It’s

✅ The dog wagged its tail.    (possessive — no apostrophe!)
✅ It's a beautiful day.       (it is)

Confusion: English uses ’s for possession with nouns (“dog’s tail”) but NOT with “its.” “It’s” always means “it is.”

3. Your / You’re

✅ Is this your coat?          (possessive)
✅ You're doing great.         (you are)

4. Affect vs Effect

✅ The weather affects my mood.    (verb — to influence)
✅ The effect was immediate.       (noun — the result)

Rule of thumb: “Affect” is almost always a verb. “Effect” is almost always a noun. (There are rare exceptions — “to effect change” — but ignore them until you’re confident.)

5. Then vs Than

✅ First we ate, then we left.           (time / sequence)
✅ She is taller than him.               (comparison)

6. Who vs Whom

✅ Who wrote this?             (subject)
✅ To whom should I address this?  (object)

Modern usage: “Who” is acceptable in most contexts. Save “whom” for formal writing.

7. Fewer vs Less

✅ Fewer people attended.      (countable — people, books, dollars)
✅ Less water is needed.       (uncountable — water, time, money as a concept)

Supermarket test: “10 items or fewer” (correct). “10 items or less” (common but wrong).

8. Me vs I

✅ She gave it to me.               (object)
✅ She and I went to the store.     (subject)
❌ She gave it to John and I.       (common error!)
✅ She gave it to John and me.      (correct — object of preposition)

Test: Remove the other person. “She gave it to I” → wrong. “She gave it to me” → right.

9. Dangling Modifiers

A modifier that doesn’t logically attach to anything in the sentence:

❌ Walking to the store, the rain started.
   (Is the rain walking?)

✅ Walking to the store, I felt the rain start.
   (Now "walking" attaches to "I.")

Fix: Ensure the subject right after the comma is the one performing the action.

10. Misplaced Modifiers

❌ I almost ate all the cookies.
   (You almost ate them but didn't? Or you ate almost all of them?)

✅ I ate almost all the cookies.

11. Subject-Verb Agreement

✅ The list of items is on the table.     (list = singular)
❌ The list of items are on the table.    (common error — "items" is plural but it's the object of the preposition)

✅ Everyone is here.                      (everyone = singular)
❌ Everyone are here.

12. Comma Splices

❌ I went to the store, I bought milk.          (two complete sentences joined by comma)
✅ I went to the store, and I bought milk.      (add conjunction)
✅ I went to the store. I bought milk.          (separate sentences)
✅ I went to the store; I bought milk.          (semicolon)

13. Apostrophe in Plurals

✅ I have three cats.             (plural — no apostrophe)
❌ I have three cat's.            (incorrect)

✅ The cat's bowl is empty.       (possessive singular)
✅ The cats' bowls are empty.     (possessive plural)

Quick Reference

Error	Fix
There/their/they’re	There = location, Their = possession, They’re = they are
Its/it’s	Its = possessive, It’s = it is
Your/you’re	Your = possessive, You’re = you are
Affect/effect	Affect = verb, Effect = noun
Then/than	Then = time, Than = comparison
Fewer/less	Fewer = countable, Less = uncountable
Dangling modifier	Put the subject right after the comma

Related: Learn show don’t tell and active vs passive voice.