30 Grammar Mistakes You‘re Probably Making (and How to Fix Them)

You may think you‘ve got a handle on grammar, but even the most educated people make common writing errors. From misplaced commas to mixed-up homophones, the English language is full of traps and pitfalls. And in the digital age, when we‘re all publishing content online, there‘s no hiding from your grammatical mistakes.

But fear not! By familiarizing yourself with these 30 frequent offenders, you can take your writing to the next level and avoid embarrassing gaffes. We‘ll break down the most common grammar errors into four categories: punctuation, word choice, sentence structure, and spelling. For each mistake, we‘ll explain the rule, give examples, and provide practical tips for getting it right.

Punctuation Problems

1. The Serial Comma Debate

The serial comma (also known as the Oxford comma) is the final comma in a list of three or more items. While some style guides consider it optional, omitting it can cause confusion. Compare these two sentences:

I love my parents, Lady Gaga and Humpty Dumpty.

I love my parents, Lady Gaga, and Humpty Dumpty.

Without the comma before "and," it sounds like Lady Gaga and Humpty Dumpty are your parents! The serial comma makes your meaning clear.

Tip: Unless your style guide says otherwise, always use the serial comma for clarity and consistency.

2. Apostrophe Catastrophes

Apostrophes have two main uses: to indicate possession and to form contractions. They should not be used to make words plural. Some common mistakes include:

Error Correction
The dog wagged it‘s tail. The dog wagged its tail.
She loves all her aunt‘s and uncle‘s. She loves all her aunts and uncles.
The 1980‘s were a great decade. The 1980s were a great decade.

Tip: To indicate possession, add an apostrophe plus s (‘s) to singular nouns and just an apostrophe (‘) to plural nouns ending in s. And never use an apostrophe to make a word plural.

3. Commas Gone Wild

Commas are used to separate clauses, items in a list, and introductory phrases. But using them incorrectly can create choppy or run-on sentences. Some frequent mistakes:

Error Correction
I like cooking my family and my pets. I like cooking, my family, and my pets.
Let‘s eat Grandma. Let‘s eat, Grandma.
After the game the team celebrated with pizza. After the game, the team celebrated with pizza.

Tip: Read your sentences aloud. If you naturally pause or need to take a breath, you probably need a comma.

4. Semicolon Stumpers

Semicolons have two main functions: to separate independent clauses and to separate items in a complex list. Many writers avoid them altogether, but when used correctly, they can add variety and sophistication to your writing.

Examples of correct semicolon usage:

I have a big test tomorrow; I can‘t go out tonight.

We need to pack a tent, sleeping bags, and food; flashlights and batteries; and a first-aid kit.

Tip: Use a semicolon when you could use a period but want to show a closer connection between two thoughts. And if the items in your list contain commas, use semicolons to separate them.

Word Choice Woes

5. Affect vs. Effect

These two words are often used interchangeably, but they have distinct meanings. Affect is usually a verb meaning to influence or impact. Effect is usually a noun meaning the result or consequence.

Error Correction
The weather effected my plans. The weather affected my plans.
The new policy will have a big affect. The new policy will have a big effect.

Tip: If you can substitute "influence" or "impact," use affect. If you can substitute "result" or "consequence," use effect.

6. Less vs. Fewer

Use less for uncountable nouns (things you can‘t individually count) and fewer for countable nouns. Time, money, and distance are often used with less, while people and objects are used with fewer.

Error Correction
There were less people at the party. There were fewer people at the party.
I have fewer money than I thought. I have less money than I thought.

Tip: If you can count it individually, use fewer. If you can‘t, use less.

7. Who vs. Whom

Who is used for subjects and whom is used for objects. If you can substitute "he" or "she," use who. If you can substitute "him" or "her," use whom.

Error Correction
Who did you invite to the party? Whom did you invite to the party?
Whom won the race? Who won the race?

Tip: Rephrase the sentence to answer it with "he/she" or "him/her." That will tell you whether to use who or whom.

8. Me, Myself, and I

Use I when it‘s the subject of the sentence, me when it‘s the object, and myself only when you‘ve already used I in the sentence and are referring back to the same person.

Error Correction
Me and Sarah went to the store. Sarah and I went to the store.
Give the report to Sarah and I. Give the report to Sarah and me.
I did the project all by myself. I did the project myself.

Tip: Take the other person out of the sentence. You wouldn‘t say "Me went to the store" or "Give the report to I," so you know to use Sarah and I / Sarah and me instead.

Sentence Structure Stumbles

9. Run-On Sentences

A run-on sentence is two or more independent clauses joined without appropriate punctuation or conjunction. They can be confusing and exhausting to read. There are a few ways to fix them:

Error: She loves coffee she drinks it every day.


  • She loves coffee. She drinks it every day. (period)
  • She loves coffee; she drinks it every day. (semicolon)
  • She loves coffee, and she drinks it every day. (comma + conjunction)

Tip: If you have two complete thoughts that could each stand alone as a sentence, make sure they‘re properly separated.

10. Sentence Fragments

On the flip side, a sentence fragment is an incomplete thought punctuated as a sentence. It may be missing a subject, verb, or complete idea.

Error Correction
Because I said so. You have to do it because I said so.
Eating ice cream on a hot day. I love eating ice cream on a hot day.

Tip: Every sentence needs a subject (the doer of the action) and a predicate (the verb and additional information). If it doesn‘t have both, it‘s not a complete sentence.

11. Dangling and Misplaced Modifiers

Modifiers are words or phrases that describe other parts of the sentence. When they‘re in the wrong place or missing key information, they can cause unintentional hilarity. Dangling modifiers don‘t clearly refer to any word in the sentence, while misplaced modifiers are too far from the word they‘re modifying.

Error Correction
After rotting in the cellar for weeks, my brother brought up some potatoes. After the potatoes rotted in the cellar for weeks, my brother brought them up.
I served sandwiches to the children on paper plates. I served the children sandwiches on paper plates.

Tip: Make sure your modifying phrases are as close as possible to the words they describe and include all the necessary information.

12. Parallel Structure Problems

Parallel structure means using the same grammatical form for words or phrases in a series. It creates a balanced, pleasing rhythm and aids comprehension. Make sure all the items in your list follow the same grammatical pattern.

Error Correction
I like hiking, swimming, and to fish. I like hiking, swimming, and fishing.
Her goals are to get promoted, to buy a house, and traveling the world. Her goals are to get promoted, to buy a house, and to travel the world.

Tip: When you have a list or comparison, check that each item starts with the same part of speech (noun, verb, etc.) and follows the same format.

Spelling Slipups

13. Their, There, and They‘re

These homophones (words that sound the same but have different spellings and meanings) are commonly confused, but they have distinct uses:

  • Their is a possessive pronoun meaning belonging to them.
  • There is an adverb specifying a place or existence.
  • They‘re is a contraction of "they are."

Some examples:

Their car is parked over there.

I hope they‘re not lost.

Tip: If you can substitute "they are," use they‘re. For the other two, determine whether you‘re indicating possession (their) or referring to a place (there).

14. You‘re vs. Your

Here‘s another set of homophones that trips people up. You‘re is a contraction of "you are," while your is a possessive pronoun meaning belonging to you.

Error Correction
Is this you‘re book? Is this your book?
I think your going to love it. I think you‘re going to love it.

Tip: Expand the contraction. If "you are" makes sense in the sentence, use you‘re. If not, it should be your.

15. Loose vs. Lose

Despite sounding similar, these two words have very different meanings. Loose is an adjective meaning not tightly fastened or too relaxed. Lose is a verb meaning to misplace something or to fail to win.

Error Correction
I always loose my keys. I always lose my keys.
This shoe is too lose. This shoe is too loose.

Tip: Loose rhymes with goose and moose. Lose rhymes with snooze and blues. If you can replace it with "not tight," use loose. If you can replace it with "misplace," use lose.

16. To, Too, and Two

To is a preposition indicating direction or purpose. Too is an adverb meaning also or excessively. Two is the number 2.

Error Correction
I‘m to tired to go out. I‘m too tired to go out.
These too books are overdue. These two books are overdue.

Tip: If you can substitute "also" or "excessively," use too. If you‘re referring to the number after one, use two. Everything else is likely to.

The Bottom Line

Good grammar isn‘t about being pedantic or showing off. It‘s about communicating your ideas clearly and professionally. In a study by Grammarly and Harris Poll, researchers found that people with fewer grammar errors in their LinkedIn profiles achieved higher positions and were promoted more frequently. And in another study of 100 native English speakers, the majority said they would be less likely to trust a website with obvious grammar mistakes.

By taking the time to learn these common errors and proofread your work, you can make a better impression on your readers, whether they‘re your boss, your customers, or your social media followers. Writing is a skill, and like any skill, it takes practice and attention to detail to master.

So next time you sit down to write, keep this list handy and challenge yourself to identify and eliminate these 30 grammar mistakes. Your writing will be stronger, clearer, and more effective as a result. And who knows? You might even start to enjoy the process of crafting the perfect sentence.

Remember, even the best writers make mistakes sometimes. The key is to learn from them and keep improving. Happy writing!