Lesson 2: Common Grammar Mistakes | Writing & Grammar

Warm-up

Everyone Makes These Mistakes

Grammar mistakes don't just happen to learners — native speakers make them too. The difference is knowing why something is wrong, so you can fix it every time.

In this lesson, you'll tackle the 8 most confusing word pairs in English, learn the subject-verb agreement traps that catch even advanced writers, and build the habit of checking your own work.

These aren't obscure grammar rules. These are the mistakes that appear in professional emails, social media, and published articles every single day.

Key Concepts

Confusing Word Pairs

Click each card to see the correct usage and a memory trick.

their / there / they're

Three words, three meanings

their = belonging to them. there = a place. they're = they are. Trick: "they're" always expands to "they are."

Tap to flip

its / it's

The #1 most common error

its = belonging to it (no apostrophe!). it's = it is. Trick: if you can replace with "it is," use it's. Otherwise, its.

Tap to flip

your / you're

Possession vs. contraction

your = belonging to you. you're = you are. "You're going to love your new job."

Tap to flip

affect / effect

Verb vs. noun (usually)

affect = verb (to influence). effect = noun (the result). "The rain will affect the event. The effect will be fewer attendees."

Tap to flip

then / than

Time vs. comparison

then = next, after that (time). than = comparison. "First do this, then that." "She is taller than her brother."

Tap to flip

fewer / less

Countable vs. uncountable

fewer = things you can count. less = things you measure. "Fewer people, less time." "Fewer mistakes, less confusion."

Tap to flip

who / whom

Subject vs. object

who = subject (does the action). whom = object (receives the action). Trick: "He did it" = who. "Give it to him" = whom.

Tap to flip

lie / lay

The hardest pair in English

lie = to recline (no object). "I lie down." Past: "I lay down yesterday." lay = to put something down (needs object). "Lay the book on the table."

Tap to flip

Key Phrases

Spot the Mistake

Each card shows a common mistake on the front. Flip to see the correction and explanation.

⚠ "The team are working hard."

Subject-verb agreement

✅ "The team is working hard." In American English, collective nouns (team, company, government) take singular verbs.

Tap to flip

⚠ "Everyone need to submit their form."

Indefinite pronoun agreement

✅ "Everyone needs to submit their form." Everyone, someone, nobody, each = singular verb. "Their" is now accepted for gender-neutral reference.

Tap to flip

⚠ "I have went to the store."

Past participle error

✅ "I have gone to the store." With "have," use the past participle: gone, done, seen, written (not went, did, saw, wrote).

Tap to flip

⚠ "She don't like coffee."

Third person singular

✅ "She doesn't like coffee." Third person singular (he/she/it) always uses "does/doesn't," not "do/don't."

Tap to flip

Sample Writing

Before & After

This paragraph contains 5 common grammar mistakes. Compare the "before" and "after" versions.

🔎

Can You Spot All 5 Errors?

Common mistakes in a professional email

✗

Dear Team, The list of updates are attached. Each member need to review it before Thursday. Its important that your aware of the changes because they will effect everyone. Than we can discuss at the meeting.

⚠ 5 errors: (1) "are" should be "is" — (2) "need" should be "needs" — (3) "Its" should be "It's" — (4) "your" should be "you're" — (5) "effect" should be "affect"

✓

Dear Team, The list of updates is attached. Each member needs to review it before Thursday. It's important that you're aware of the changes because they will affect everyone. Then we can discuss at the meeting.

✅ All 5 errors fixed: is (subject-verb), needs (each = singular), It's (it is), you're (you are), affect (verb).

Pattern Spotlight

Subject-Verb Agreement Traps

The most common agreement trap: the verb agrees with the SUBJECT, not the nearest noun. Prepositional phrases between the subject and verb often cause confusion.

💡 Tricky Subject-Verb Agreement

⚠ Wrong	✅ Right	Why
"The list of items are long."	"The list of items is long."	Subject = "list" (singular), not "items."
"One of the students have finished."	"One of the students has finished."	Subject = "one" (singular), not "students."
"The box of chocolates were delicious."	"The box of chocolates was delicious."	Subject = "box" (singular), not "chocolates."
"Neither the manager nor the employees was happy."	"Neither the manager nor the employees were happy."	With "neither...nor," the verb agrees with the nearer subject ("employees" = plural).

Quick Test

Cross out the prepositional phrase. What's left? That's your subject. Match the verb to it.

💡

Pro Tip

Don't rely solely on grammar checkers. They catch surface errors, but they can't explain why something is wrong. Understanding the rule is more valuable than auto-correcting it. When you know why "the list of items is long" is correct, you'll never make that mistake again — in any sentence, in any context, without needing a tool.

Practice

Test What You've Learned

Complete these exercises to practise spotting and fixing common grammar mistakes.

Multiple Choice Exercise 1 of 4

Which sentence is correct?

The number of applicants has increased this year.

The number of applicants have increased this year.

The number of applicants are increasing this year.

The number of applicants were increased this year.

🎉

Correct! "The number" is singular, so it takes "has." Don't be tricked by "applicants" — it's inside a prepositional phrase and isn't the subject.

💡

Not quite. The correct answer is A. "The number" is the subject (singular), so it takes "has." Cross out "of applicants" to find the real subject.

Fill in the Blank Exercise 2 of 4

Choose the correct form: "___ been a long day, and the team has finished its work."

been a long day, and the team has finished its work.

🎉

Excellent! "It's" = "it is." Notice that "its" later in the sentence has no apostrophe because it shows possession (the team's work).

💡

Almost! The answer is "It's" (= "it is"). Remember: if you can replace with "it is," use the apostrophe. The second "its" is possessive (no apostrophe).

Multiple Choice Exercise 3 of 4

Which sentence uses "affect" and "effect" correctly?

The new policy will effect everyone in the company.

The affect of the storm was devastating.

How will this effect our timeline?

The changes will affect productivity. The effect will be significant.

🎉

Perfect! "Affect" is the verb (to influence) and "effect" is the noun (the result). "The changes will affect productivity. The effect will be significant."

💡

Not quite. The correct answer is D. Remember: affect = verb (A for Action), effect = noun (E for End result).

Word Order Exercise 4 of 4

Arrange these words into a grammatically correct sentence:

assignment

has

Each

their

completed

students

the

🎉

You got it! "Each of the students has completed their assignment." "Each" is singular so it takes "has," and "their" works as a gender-neutral pronoun.

💡

Close! The correct order is: "Each of the students has completed their assignment." "Each" = singular subject, so use "has."

Key Takeaways

8 confusing pairs: their/there/they're, its/it's, your/you're, affect/effect, then/than, fewer/less, who/whom, lie/lay.

Subject-verb agreement: the verb matches the subject, not the nearest noun. Cross out prepositional phrases to find it.

it's vs. its: if you can replace with "it is," use the apostrophe. Otherwise, no apostrophe.

affect vs. effect: affect = verb (action), effect = noun (end result).

Understanding beats auto-correct. Know the rule, and you'll never make the mistake again.

Everyone, each, nobody = singular. They take singular verbs (has, needs, is).

Lesson 1: Sentence Structure Lesson 3: Punctuation