Grammar Checker: Most Common English Grammar Mistakes and How to Fix Them

The 20 Most Common Grammar Mistakes

Its vs It's

Its: Possessive (The company lost its way). It's: Contraction of "it is" or "it has" (It's raining).

Your vs You're

Your: Possessive (Your bag is here). You're: Contraction of "you are" (You're welcome).

There vs Their vs They're

There: A place or direction (Over there). Their: Possessive (Their house). They're: "They are" (They're here).

Effect vs Affect

Effect: Usually a noun — the result (The effect was significant). Affect: Usually a verb — to influence (This affects everyone).

Then vs Than

Then: Relates to time (First this, then that). Than: For comparisons (Better than expected).

Less vs Fewer

Fewer: For countable things (Fewer people attended). Less: For uncountable quantities (Less sugar).

Could of vs Could have

"Could of" is always wrong. The correct form is "could have," "would have," "should have."

Comma splice

Incorrect: I went to the store, I bought milk.

Correct: I went to the store. I bought milk. OR: I went to the store, and I bought milk.

Dangling modifier

Incorrect: Running down the street, the keys fell from my pocket.

Correct: As I ran down the street, the keys fell from my pocket.

Subject-verb disagreement

Incorrect: The team are playing well.

Correct: The team is playing well. (In American English, collective nouns take singular verbs)

Apostrophe in plurals

Incorrect: Three apple's. Banana's for sale.

Correct: Three apples. Bananas for sale.

Double negatives

Incorrect: I don't have nothing to say.

Correct: I don't have anything to say. OR: I have nothing to say.

Who vs Whom

Who: Subject (Who called?). Whom: Object (To whom did you speak?). Test: Replace with he/him — if "he" sounds right, use who; if "him" sounds right, use whom.

Split infinitive debate

"To boldly go" is technically a split infinitive. Most modern style guides accept it when avoiding it sounds awkward.

Passive voice overuse

Passive: The mistake was made by the team. Active: The team made the mistake. Active voice is usually clearer and more direct.