# Common grammar mistakes and how to correct them

> Common grammar mistakes in English include confused words (its and it's; their, there and they're; then and than), agreement errors (the list of items are), verb forms that do not exist (could of), comma splices and apostrophes in plurals. This page lists twenty of them with corrections and reasons, free to read, and sample texts to try in the checker.

Twenty mistakes that turn up in emails, essays and reports, each with the correction and the reason. Read them for free, or paste your own text into the checker.

## At a glance

- **Examples:** 20, in four groups, each with the correction
- **Free to read:** Every example and reason on this page
- **Sample texts:** 6 short texts with several mistakes each
- **Price:** 1 credit per word, 20-credit minimum; $0.08 to $0.20 per 1,000 words
- **Account:** Free to sign up; checks use purchased credits

- 20 corrections
- Reasons in plain English
- Sample texts to try

[Check my text](https://grammarcheckerai.app/create)

## Four kinds of mistakes

- **Confused words**: Words that sound alike but mean different things: its and it's, affect and effect, lose and loose.
- **Agreement and verb forms**: A verb that does not match its subject, or a form that does not exist, such as could of.
- **Punctuation**: Comma splices, missing commas after an opening word, and apostrophes in plurals.
- **Sentence structure**: Fragments, run-on sentences and opening phrases that describe the wrong subject.

## How to find these mistakes in your own writing

1. **Scan for the pairs**: Search your text for its, their, then, your and affect, and check each one.
2. **Match each verb**: Find the subject of every verb, skipping the words in between.
3. **Check with the tool**: Paste the text; the list of fixes names each mistake and the rule behind it.

## Confused words

Each line shows the mistake, the correction and the reason:

- The company lost it's best client → The company lost its best client (its is possessive; it's means it is)
- Their going to call → They're going to call (they're means they are)
- Sales were better then expected → Sales were better than expected (than compares; then is about time)
- The change will effect sales → The change will affect sales (affect is the verb; effect is usually the noun)
- Don't loose the receipt → Don't lose the receipt (lose means misplace; loose means not tight)

## Agreement and verb forms

The verb must match its subject, and some common forms do not exist:

- The list of items are long → The list of items is long (the subject is list, not items)
- Me and Sarah went → Sarah and I went (use I for the subject)
- We should of left earlier → We should have left earlier (could, should and would take have)
- There is three options → There are three options (the verb matches three options)
- Less people came → Fewer people came (fewer for things you can count)

## Punctuation

Punctuation mistakes change how a sentence reads, and sometimes what it means:

- It was late, we went home → It was late, so we went home (a comma alone cannot join two sentences)
- However the plan changed → However, the plan changed (a comma follows an opening word)
- Apple's for sale → Apples for sale (plurals take no apostrophe)
- Lets meet on friday → Let's meet on Friday (let's means let us; days take capitals)
- The teams report → The team's report (a possessive needs an apostrophe)

## Sentence structure

These mistakes are about how a sentence is built rather than single words:

- Because the train was late. → Because the train was late, I missed the meeting. (a because clause cannot stand alone)
- I finished the report I sent it to Anna → I finished the report and sent it to Anna (two sentences run together)
- Walking to work, the rain started → Walking to work, I got caught in the rain (the opening phrase must describe the subject)
- If I would have known, I would have come → If I had known, I would have come (the if clause takes had)
- The reason is because it rained → The reason is that it rained (the reason is that, not because)

## Sample texts to check

Each sample has several of the mistakes above. Copy one, or press Try it to open it in the checker.

### Emails

- **Follow-up:** Hi Mark, I wanted to follow up on my email from last week, I haven't heard back yet. Me and my colleague would like to know if your available for a call on thursday. Let me know what time works for you.
- **Apology:** Dear Ms. Lee, we are sorry for the delay with you're order. There was three items missing from the shipment and we should of noticed it sooner. A replacement will arrive on Monday.

### School

- **Essay paragraph:** The novel shows how the main character changes over time. At first she is afraid to speak, however by the end she leads the protest. The reason is because her friends trusts her, and their support effect every decision she makes.
- **Lab report:** The results was better then we expected. Less samples failed than in the first test, and the error rate dropped to 2 percent. Its possible that the new method reduce contamination.

### Work

- **Status update:** The project is on track, we finished the design phase on Tuesday. The team still has three task left and the client want a demo next week. Lets plan the demo together on monday.
- **Release note:** This version fix the login bug and make the app faster. Users can now export there data to CSV. If you would of updated earlier, you would have seen the new menu already.


## More checkers

- [Punctuation and grammar checker](https://grammarcheckerai.app/punctuation-checker): Commas, apostrophes and capitals, with every fix explained.
- [AI grammar checker](https://grammarcheckerai.app/): The checker in six languages, and what is free on this site.
- [ChatGPT grammar checker](https://grammarcheckerai.app/chatgpt-grammar-checker): A proofreading prompt you can copy into any chatbot.

## Grammar checker pricing by the word

- Starter: $7.99 / month, 75,000 credits
- Pro: $19.99 / month, 200,000 credits
- Business: $49.99 / month, 600,000 credits
- Small: $4.99, 25,000 credits
- Medium: $14.99, 100,000 credits
- Large: $34.99, 300,000 credits

## Common grammar mistakes FAQ

### What is the most common grammar mistake?

There is no single answer that holds for every writer, but confused words such as its and it's, subject-verb agreement and comma splices turn up again and again in everyday English. The examples on this page cover all three.

### How can I avoid grammar mistakes in my writing?

Read the text aloud, search for the word pairs you tend to confuse, check that each verb matches its subject, and leave some time between writing and checking. A grammar checker helps with routine mistakes, but read its fixes before you accept them.

### Is it wrong to start a sentence with and or but?

No. Most modern style guides accept it; it is a matter of style rather than grammar. With proofread, the checker is told to leave such sentences as they are.

### Can I check my text for these mistakes for free?

The examples and corrections on this page are free. Automated checks use purchased credits: 1 credit per word, at least 20 credits per check, and new accounts start with no credits.

## Find these mistakes in your own text

Packs start at $4.99 for 25,000 credits. Signing up is free; checks use purchased credits.

_Last updated 2026-10-23_