10 Common English Grammar Mistakes

Improve common English errors by checking the sentence’s subject, verb form, reference and context. Compare each correction with the intended meaning.

Everyone makes grammar mistakes – even native English speakers! Let's look at the 10 most common ones and learn how to fix them. 🔧

1. Who vs. Whom

Who = subject (doing the action). Whom = object (receiving the action). Trick: If you can replace with 'he/she', use WHO. If 'him/her', use WHOM.

❌ Whom is calling? → ✅ Who is calling?

💡 He is calling (subject) → use WHO

❌ Who did you call? → ✅ Whom did you call?

💡 You called him (object) → use WHOM

❌ Whom ate the cake? → ✅ Who ate the cake?

💡 She ate the cake (subject) → use WHO

❌ Who should I talk to? → ✅ Whom should I talk to?

💡 Talk to him (object) → use WHOM

2. Their vs. There vs. They're

Their = belongs to them. There = a place. They're = they are.

Their house is big.

💡 Belongs to them

Put the book over there.

💡 A location

They're coming to the party.

💡 They are coming

❌ There car is new. → ✅ Their car is new.

💡 The car belongs to them

❌ Their going home. → ✅ They're going home.

💡 They are going

3. Its vs. It's

Its = belongs to it (no apostrophe!). It's = it is or it has.

The dog wagged its tail.

💡 Tail belongs to the dog

It's raining outside.

💡 It is raining

❌ Its a beautiful day. → ✅ It's a beautiful day.

💡 It is a beautiful day

❌ The cat licked it's paw. → ✅ The cat licked its paw.

💡 Paw belongs to the cat

4. Effect vs. Affect

Affect = verb (action). Effect = noun (result). Remember: A for Action, E for End result!

The rain will affect the game.

💡 Affect is the action verb

The effect was amazing.

💡 Effect is the result (noun)

❌ The medicine had no affect. → ✅ The medicine had no effect.

💡 Result = effect (noun)

❌ This will effect your grade. → ✅ This will affect your grade.

💡 Action = affect (verb)

5. Then vs. Than

Then = time or sequence. Than = comparison.

First eat, then play.

💡 Sequence of events

She is taller than me.

💡 Comparing two things

❌ He is smarter then her. → ✅ He is smarter than her.

💡 Comparing = than

❌ We ate, than we left. → ✅ We ate, then we left.

💡 Sequence = then

6. Loose vs. Lose

Loose = not tight (rhymes with 'goose'). Lose = to misplace or fail (rhymes with 'choose').

My pants are too loose.

💡 Loose = not tight (adjective)

Don't lose your keys!

💡 Lose = to misplace (verb)

❌ I don't want to loose the game. → ✅ I don't want to lose the game.

💡 Lose = to fail

❌ The knot is too lose. → ✅ The knot is too loose.

💡 Loose = not tight

7. Fewer vs. Less

Fewer = things you can COUNT (apples, people, books). Less = things you can't count (water, time, money).

❌ I have less friends. → ✅ I have fewer friends.

💡 You can count friends → use FEWER

I have less time today.

💡 Time is uncountable → use LESS

❌ There are less students today. → ✅ There are fewer students today.

💡 Students are countable → use FEWER

She earns less money than before.

💡 Money (concept) is uncountable → use LESS

8. Your vs. You're

Your = belongs to you. You're = you are.

Is this your book?

💡 The book belongs to you

You're very kind.

💡 You are very kind

❌ Your the best! → ✅ You're the best!

💡 You are the best

❌ You're phone is ringing. → ✅ Your phone is ringing.

💡 The phone belongs to you

❌ Is you're sister coming? → ✅ Is your sister coming?

💡 Sister belongs to you

9. Lie vs. Lay

Lie = to recline (no object needed). Lay = to put something down (needs an object).

I need to lie down.

💡 Lie = recline yourself (no object)

Lay the book on the table.

💡 Lay = put the book (object) down

❌ I will lay down for a nap. → ✅ I will lie down for a nap.

💡 No object = use lie

❌ Please lie your bag here. → ✅ Please lay your bag here.

💡 Bag is the object = use lay

The hen lays eggs.

💡 Eggs are the object

10. Could of / Should of / Would of

This is ALWAYS wrong! The correct forms are could have, should have, would have (or could've, should've, would've).

❌ I could of helped. → ✅ I could have helped.

💡 Could have (could've)

❌ You should of called me. → ✅ You should have called me.

💡 Should have (should've)

❌ We would of won. → ✅ We would have won.

💡 Would have (would've)

❌ They must of forgotten. → ✅ They must have forgotten.

💡 Must have (must've)

Continue learning

A, An and The: English Article Rules · subject verb agreement exercises