Most Common English Grammar Mistakes to Watch Out For

Grammar mistakes aren’t a sign that someone is “bad” at English — they’re a normal part of using a complicated and often inconsistent language. Even native speakers get tripped up sometimes, especially when writing quickly or navigating tricky homophones. What’s more important than perfection is awareness — being able to spot what’s off, explain why it’s off, and confidently correct it.

This is especially true if you plan to teach English abroad. When students ask, “Why is it fewer potatoes but less rice?” or “Should I say me or I here?” — it helps to have more than just instinct. As a TEFL teacher, you’ll be a language model, a grammar guide, and sometimes a myth-buster. The more clearly you can explain the logic behind English usage, the more empowered your students will feel — and the more confident you’ll be in the classroom.

Confusing Homophones: There / Their / They’re

This trio is one of the most commonly confused sets in English — even among native speakers who write fast or don’t proofread. Why? Because they all sound exactly the same.

Here’s the breakdown:

• There refers to a place or position.
  Example: The books are over there on the table.
• Their is a possessive adjective. It shows ownership.
  Example: That’s their house on the corner.
• They’re is a contraction of “they are.”
  Example: They’re going to the park later.

A quick trick:

Whenever you see “they’re,” try replacing it with “they are.” If it doesn’t make sense, you’ve used the wrong word.

🔁 They’re coming to dinner → They are coming to dinner ✅
🚫 Their coming to dinner → doesn’t work.

This is a small mistake that can really trip students up in writing. Teaching them to test substitutions aloud can build both confidence and clarity.

Affect vs. Effect: Verb or Noun?

This one’s sneaky because the difference is subtle — and there are exceptions. But for most everyday uses, here’s the rule:

• Affect is usually a verb, meaning to influence or change.
  Example: The loud music affected my concentration.
• Effect is usually a noun, meaning the result or outcome.
  Example: The new policy had a positive effect on attendance.

Memory tip:

Think “Affect = Action.” Both start with “A,” and “action” reminds you that it’s a verb.

Of course, English wouldn’t be English without exceptions:

• To effect change is a valid use, where “effect” becomes a verb meaning to bring about.
• He showed no affect is a rare but correct use of “affect” as a noun in psychology, meaning emotion or expression.

But unless you’re deep into academic or clinical English, you likely won’t need those exceptions often. For TEFL classrooms, stick with the basic pattern and give your students practical examples.

Me vs. I: Getting Object and Subject Right

Here’s a classic case of people overcorrecting. Somewhere along the way, “and I” started to sound more formal, and now it shows up in places it doesn’t belong.

Let’s clear it up:

• I is a subject pronoun (used when “you” are doing the action).
  Example: Sarah and I went to the market.
• Me is an object pronoun (used when something is being done to you).
  Example: The teacher gave the papers to Sarah and me.

The quick test:

Remove the other person and read the sentence again.

🚫 Can you send that email to James and I?
→ Can you send that email to I? ❌ (Wrong)
✅ Can you send that email to James and me?

This one comes up a lot in speaking, especially in polite or formal situations. As a teacher, it’s useful to help students trust the grammar more than the “sound” — and practice using pronouns in different positions with real-life examples.

Its vs. It’s: The Contraction Trap

Possessives in English can be tricky — especially when they look like contractions. Its and it’s are a classic example. The confusion makes sense: most possessives end in 's, so why doesn’t its?

Here’s the breakdown:

• It’s is a contraction of “it is” or “it has.”
  Example: It’s going to rain later.
  Example: It’s been a long week.
• Its is the possessive form of it — used to show ownership.
  Example: The cat licked its paw.

The test:

Swap in “it is” or “it has.” If it works, use it’s. If not, use its.

🚫 The company lost it’s license.
→ The company lost it is license. ❌
✅ The company lost its license.

Even advanced students (and many native speakers) mix these up, especially in writing. Helping learners master this distinction early builds confidence in both reading and writing.

Less vs. Fewer: Countable vs. Uncountable Nouns

This one’s a grammar rule that many native speakers ignore, but it’s still worth teaching — especially for students preparing for formal exams or academic writing.

The rule:

• Fewer is for countable nouns (things you can count).
  Example: Fewer students attended class today.
• Less is for uncountable nouns (things measured in bulk).
  Example: There’s less water in the bottle.

The trick:

Can you add “s” to the noun or count it with a number?

• Carrots → plural → fewer carrots
• Rice → uncountable → less rice

🚫 10 items or less — grammatically incorrect, but common.
✅ 10 items or fewer — the formal choice.

The grammar is simple, but usage in the real world is inconsistent. That gives you a great teaching moment: English isn’t always logical, but understanding the rules helps students use the language with more precision.

Who vs. Whom: The Grammar Rule Everyone Forgets

This one tends to intimidate learners — and let’s be honest, lots of fluent speakers avoid it entirely. But it doesn’t have to be scary.

The rule:

• Who is used as the subject (the one doing the action).
  Example: Who is calling?
• Whom is used as the object (the one receiving the action).
  Example: To whom should I speak?

Quick trick:

Replace with he/she or him/her.

• Who/whom called you?
  → He called me → use who

• Who/whom did you call?
  → I called him → use whom

In casual speech, most people just say who. You won’t sound wrong for skipping whom in everyday conversation — but it still has a place in formal writing and exams. Teaching the distinction helps your students become more versatile and confident in both.

Farther vs. Further: Physical vs. Figurative Distance

English draws a subtle line between farther and further, but it’s one that often gets blurred — especially across regions.

The rule of thumb:

• Farther refers to physical distance.
  Example: She ran farther than anyone else in the class.
• Further is more abstract — used for figurative or metaphorical distance.
  Example: We need to discuss this further.

Regional note:

In American English, this distinction is more emphasized. In British English, further is often used for both.

That said, the difference is rarely critical — and most people won’t even notice in casual use. But for your more advanced students, especially those writing essays or taking proficiency exams, understanding this nuance adds polish to their English.

i.e. vs. e.g.: Clarify vs. Give Examples

These two little abbreviations confuse a lot of people — and they matter more than you think, especially in writing.

• i.e. means that is (from Latin id est). Use it to clarify or restate something in a different way.
  Example: I love traditional desserts — i.e., ones made from scratch using family recipes.

• e.g. means for example (from Latin exempli gratia). Use it when you want to list one or more examples.
  Example: I love traditional desserts — e.g., apple pie, tiramisu, baklava.

Why it matters:

Mixing them up can confuse your meaning. You don’t want to accidentally limit what you say when you meant to expand on it.

💡 Spoken English tip: in everyday conversation, just say “for example” or “in other words.” You’ll sound more natural, especially with learners.

Which vs. What: Options and Open-Ended Questions

These two question words seem interchangeable — and sometimes they are. But there’s a subtle distinction that becomes useful for learners.

• Which is used when there are a limited number of known options.
  Example: Which dessert do you want — cake or ice cream?

• What is for broader or open-ended questions.
  Example: What do you usually eat for breakfast?

Classroom tip:

If a student asks, “What is your favorite movie — The Matrix or Inception?”, you can gently guide them to use which in that context.

That said, don’t overcorrect. Even native speakers switch between these two freely, especially in casual conversation. Focus more on helping students understand the nuance than enforcing a rigid rule.

Lose vs. Loose: One Letter, Big Difference

This is one of those mistakes that doesn’t show up much in speech — but it’s easy to spot (and make) in writing.

• Lose is a verb — it means to misplace something or not win.
  Example: Don’t lose your keys again!

• Loose is an adjective — it means not tight or not fixed in place.
  Example: This shirt is too loose on me.

Pronunciation trick:

• Lose rhymes with snooze.
• Loose rhymes with moose.

📝 It’s a small spelling error, but it makes a big difference in meaning. Encouraging your students to sound the words out or visualize the rhymes can help lock it in.

Bonus: How to Build Confidence with Grammar

Even the best teachers — native or not — review grammar regularly. The key isn’t perfection. It’s clarity and confidence when helping your students.

Here’s how to strengthen your grammar muscles:

• Don’t rely solely on what “sounds right” — dig into the why.
• Use real-life examples, visual diagrams, or funny analogies to make explanations stick.
• Practice explaining grammar out loud — it helps you prepare for student questions.
• Take a solid TEFL grammar course if you feel rusty. It’s worth the investment.

Teaching grammar isn’t about being a walking textbook — it’s about helping your learners see patterns, stay curious, and feel confident using the language.

Conclusion

Grammar mistakes happen to everyone — even experienced teachers. But understanding why these errors happen (and how to explain them) is what sets confident TEFL teachers apart.

You don’t need to be a grammar wizard. You just need to be ready with clear, simple answers and a sense of humor. The more you teach, the better you’ll get — and your students will thank you for every “aha!” moment along the way.

Whether you're reviewing grammar for yourself or preparing to teach it abroad, remember: every little rule you learn is one more way to connect with your students and help them grow.