Common Grammar Mistakes and How to Fix Them

Even experienced writers make these grammar mistakes. Here’s a practical guide to fixing the most common errors with clear examples and simple tests you can apply immediately.

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.”

Memory Trick

“Their” contains “heir” — as in, the heirs to the property (possession). “There” contains “here” — pointing to a location. “They’re” is the only one with an apostrophe, which signals a contraction. When in doubt, expand “they’re” to “they are” in your head — if the sentence still reads correctly, use “they’re.”

Common Confusion

❌ There going to the store.         (wrong - should be "they're")
❌ Their is a problem.               (wrong - should be "there")
❌ They're dog is barking.           (wrong - should be "their")

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.”

Why This Rule Exists

This is the most confusing possessive in English because it breaks the normal rule. “Its” (without apostrophe) is the possessive form of “it,” following the same pattern as “his” and “hers” — none of which use apostrophes for possession. “It’s” (with apostrophe) is a contraction, following the pattern of “he’s” and “she’s.”

✅ The company updated its privacy policy.       (possessive)
✅ It's important to read the documentation.      (it is)
❌ The cat licked it's paw.                       (wrong)

Test: Replace with “it is.” If the sentence works, use “it’s.” If not, use “its.”

3. Your / You’re

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

❌ Your the best.               (wrong - should be "you're")
❌ You're shoes are untied.     (wrong - should be "your")

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

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.)

Real-World Examples

✅ The new policy affected employee morale.       (verb)
✅ The policy had a positive effect on morale.    (noun)
✅ The medication affects blood pressure.         (verb)
✅ The side effects include drowsiness.           (noun)

The Rare Exceptions

“To effect change” means “to bring about change” — here “effect” is used as a verb. In psychology, “affect” can be a noun meaning emotional expression: “The patient displayed a flat affect.” These exceptions are rare enough that you’ll encounter them mostly in academic or legal writing.

Test: If you can replace it with “result,” use “effect” (noun). If you can replace it with “influence,” use “affect” (verb).

5. Then vs Than

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

❌ I'd rather walk then drive.           (wrong - should be "than")
❌ We finished than went home.           (wrong - should be "then")

Test: If the sentence involves a sequence of events, use “then.” If it’s a comparison between two things, use “than.”

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.

The He/Him Test

If you can replace the word with “he” (subject), use “who.” If you can replace it with “him” (object), use “whom.”

✅ Who called you?            → He called me.        (subject → "who")
✅ You called whom?           → You called him.      (object → "whom")
✅ Who do you trust?          → You trust him?       (informal, "whom" would be strictly correct)

In informal writing and speech, “who” is increasingly used in object position. Reserve “whom” for formal documents, cover letters, and academic papers.

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).

When It Gets Tricky

• Money: “I have less than $10” (correct — money as an amount) vs “I have fewer than 10 dollar bills” (correct — individual bills)
• Time: “Less time” (correct) but “Fewer hours” (correct — hours are countable)
• Distance: “Less than 5 miles” (correct — distance as a concept)

Test: Can you count it with numbers? “Three people” → fewer. “Some water” → less.

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.

Why People Get This Wrong

Many people were told in school that “and I” sounds more formal and correct. This overcorrection leads to errors like “between you and I.” The rule is simple: “I” performs the action (subject), “me” receives the action (object).

❌ Please join John and I for dinner.           (wrong - "join I" doesn't work)
✅ Please join John and me for dinner.          (correct)
✅ John and I are hosting the dinner party.     (correct - "I" is the subject)

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.

More Examples

❌ Having finished the report, the desk was a mess.        (the desk finished the report?)
✅ Having finished the report, I found the desk was a mess.

❌ Written in haste, the author regretted the email.       (the author was written in haste?)
✅ Written in haste, the email was full of errors.

❌ To install the software, the CD must be inserted.       (the CD installs the software?)
✅ To install the software, insert the CD.

Always check that the noun immediately after the introductory phrase is the one doing 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.

Precision Matters

❌ He only reads the documentation when something breaks.
   (He doesn't do anything else with the documentation except read it?)

✅ He reads the documentation only when something breaks.
   (Clarifies: he doesn't read it proactively.)

❌ She nearly failed every exam.
   (She nearly failed them but passed?)

✅ She failed nearly every exam.
   (Clarifies: she failed most exams.)

Place modifiers directly before the word or phrase they modify. “Only,” “almost,” “nearly,” “just,” and “even” cause the most trouble — moving them even one word can change the sentence’s meaning entirely.

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.

Tricky Cases

✅ Neither the manager nor the employees are satisfied.    (verb agrees with closest subject)
✅ Neither the employees nor the manager is satisfied.     (verb agrees with closest subject)
✅ The team is meeting today.                              (collective noun = singular)
✅ The team are divided on the issue.                      (collective noun acting as individuals)

For “either/or” and “neither/nor,” the verb agrees with the subject closest to it. Collective nouns (“team,” “committee,” “family”) take singular verbs when acting as a unit and plural verbs when acting as individuals. In American English, collective nouns are usually singular; British English often uses plurals.

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)

Recognizing Comma Splices

A comma splice happens when you join two independent clauses (complete sentences) with only a comma. Three ways to fix it:

1. Add a coordinating conjunction (and, but, or, so, for, yet)
2. Split into separate sentences with a period
3. Use a semicolon (for closely related ideas)

❌ The server is down, we can't deploy.                      (comma splice)
✅ The server is down, so we can't deploy.                   (conjunction)
✅ The server is down. We can't deploy.                      (separate sentences)
✅ The server is down; we can't deploy.                      (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)

The Golden Rule of Apostrophes

Apostrophes in English serve two purposes: contractions and possession. Never use an apostrophe for plurals. If you’re making a word plural (more than one), just add -s or -es with no apostrophe.

✅ I have two dogs.
❌ I have two dog's.
✅ The 1990s were a decade of change.
❌ The 1990's were a decade of change.    (common but unnecessary apostrophe)
✅ All the CEOs attended the conference.
❌ All the CEO's attended the conference.

Quick Reference

Final Pro Tip

Even the best writers make mistakes. Professional editors use style guides (AP Style, Chicago Manual of Style, Strunk & White) for consistency. Before publishing important writing, use a grammar checker like Grammarly, ProWritingAid, or the built-in checkers in Google Docs or Microsoft Word. These tools catch the majority of the errors listed here automatically.

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

Frequently Asked Questions

What should I read to understand common grammar mistakes better?

Start with foundational works that established the field, then move to contemporary scholarship. Critical editions with annotations provide valuable context. Academic journals offer current research and debates. Reading primary sources alongside secondary analysis deepens understanding of both the works and their interpretation.

How do scholars analyze works in this category?

Analysis approaches include close reading, historical contextualization, theoretical frameworks, and comparative study. Scholars examine elements such as structure, style, themes, character development, and cultural context. Multiple readings often reveal new insights that were not apparent on first encounter.

Why is common grammar mistakes important to understand?

Literature and arts reflect and shape human experience, offering insights into different cultures, historical periods, and ways of thinking. Engaging with serious works develops critical thinking, empathy, and communication skills. The study of literature enriches personal understanding and connects us to shared human experiences across time and place.