The 30 Most Common Grammar Mistakes (and How to Avoid Them)

Writing is an art form, but also a technical skill.

I don’t subscribe to the view that great writing requires perfect grammar. In my view, great writing is more about being engaging, persuasive, and original, than absolute technical proficiency.

While perfect grammar won’t necessarily make you a great writer, it’s still important to understand the rules. If you’re trying to get an article published in an online magazine, sell copies of your e-book, or get top marks for an academic essay or thesis, poor grammar hurts. Proofreading your work if you don’t know the rules.

Fairly or not, grammar mistakes create the impression of poor attention to detail and rushed writing. If they’re too frequent, the reading experience will suffer.

Here’s a list of the 30 most common grammar mistakes that writers make and how you can avoid them.

1. There/Their/They’re

Homonyms (words that sound alike) are responsible for many of the most common grammar mistakes and the “There/Their/They’re” conundrum has tripped up almost everyone at some point. “There” refers to a place. “Their” is the possessive adjective, used before a noun. “They’re” is the contraction of “they are.” Here’s all of them in one sentence:

“They’re not happy that their drink order is still sitting on the bar over there.”

2. Effected/Affected

“Affect” is the verb meaning “to change or influence” while “effect” is the noun indicating that a change has occurred. The part that confuses most writers is the fact that the past participle of “effect” is also a verb, meaning to “produce or bring about.” Check out the difference:

“The board of directors was so profoundly affected by the advocate’s speech that they effected changes to the laws immediately.”

Yep, this can be a tough one to get right.

3. Anything with a Semicolon

The semicolon is the most widely abused punctuation mark in the English language. In its most simple form, the semicolon is used to link two related independent clauses together in one sentence. For example:

Correct: “Mark was obsessed with his hair; he used more styling products than his wife.”

While these two clauses could technically stand on their own, a writer might opt for a semicolon stylistically rather than breaking them into two sentences with a period. The big no-no comes when writers stick a conjunction in there right along with the semicolon:

Incorrect: “Mark was obsessed with his hair; and he used more styling products than his wife.”

Semicolons are also commonly misused in place of commas because both can be used when a writer is making lists. But commas can lead to the nasty “comma splice” (we’ll talk about that next) and sometimes semicolons are the only cure. Check out how beautifully semicolons save this potentially disastrous sentence:

“Greg cooked a three course meal which included an endive salad, his personal favourite; a pot roast, garnished with potatoes and carrots; and a homemade crème brûlée, crafted with his personal culinary blowtorch tool.”

4. It’s Not Nice to Splice

The comma splice will drive any writer straight down the track to “Run-On Sentence City.” Check out the sentence from above without semicolons and you’ll see an example of this most heinous of grammatical crimes:

“Greg cooked a three course meal which included an endive salad, his personal favourite, a pot roast, garnished with potatoes and carrots, and a homemade crème brûlée crafted with his own personal culinary blowtorch tool.”

5. It’s vs. Its

In fairness to all the writers out there who have made this mistake, let’s admit this can be confusing. “It’s” with an apostrophe is only to be used as the contraction “it is,” but the apostrophe screams “I’m a possessive noun!” In this case though, “Its” with no apostrophe is the possessive form.

Example: “It’s pretty clear that a zebra can’t change its stripes.”

6. The Split Infinitive

Adverbs are a beautiful thing, as long as they’re in the right place, and the right place is usually right after the infinitive form of the verb.

Correct: To study diligently

Incorrect: To diligently study

We know what you’re thinking. Yes, there are some very famous examples of this rule being broken, most notably when Star Trek’s Captain Kirk stated that his crew’s mission was “to boldly go where no man has gone before.”

Down here on Earth, though, it’s best to keep your adverbs in place and don’t break up the infinitive party.

7. Who/Whom

Even the most experienced writers find themselves hitting the reference books to get this one right. The easiest way to figure out which one you need is by answering the question you’re asking with “he,” “him,” “she,” or “her.”

If the answer is “he” or “she,” then use “Who.”

Example: “Who broke my computer?”

“She did.”

If the answer is “him” or her,” then use “whom”:

Example: “Whom are you looking for?”

“I’m looking for him.”

One easy way to remember is that both “him” and “whom” end with “m,” and they go together like peanut butter and jelly. Mmmmm. That sounds good.

8. Your/You’re

Here’s another example of the “sound alike follies.” “Your” is the possessive adjective and “You’re” is the contraction version of “You are.” Don’t let the apostrophe lure you into thinking it’s the possessive one.

9. “I” or “Me”?

It’s not always all about you. Sometimes it’s about “me”—or “I.” The head trip over whether to use “I” or “me” has been the bane of the writer’s existence since the English language first hit the page. You’ll often read writers with the best of intentions misusing “I” in an effort to be proper.

Incorrect: “She had a great time with Cindy and I.”

Choosing the correct one is all about determining whether you’re referring to a subject or an object. If it’s a subject, use “I.” If it’s an object, use “me.” In this case, “me” is an object of the preposition “with.”

If you’re looking to simplify things for yourself, try simplifying the sentence. You wouldn’t say: “She had a great time with I.” You’d say: “She had a great time with me.”

10. Less or Fewer

When you’re trying to decide between “less” and “fewer” first ask yourself: am I talking about a specific number of things? If you are, then use fewer. If not, then use “less.” If you’ve got a big bowl of salad and you can’t eat it all, you might ask for “less salad.”

If, however, there is a specific number of tomatoes in the salad and you think there are too many, you would ask for “fewer” tomatoes.

11. Allude or Elude

“Allude” with an “a” means to make a reference to something, while “elude” with an “e” means to avoid or escape. An easy way to remember the difference is that both “elude” and “escape” begin with an “e.”

12. i.e. vs e.g.

It’s time for a quick Latin lesson. “I.e” is an abbreviation of “id est,” a Latin phrase meaning “that is.” “I.e.” is used to specify something.

“I just went to my favorite fast food restaurant, i.e., Hungry Jack’s.”

“E.g.” translates to “exempli gratia” and essentially just means “for example.” Check out the difference:

“There were many fast food options at the food court, e.g. Hungry Jack’s.”

The “e” in “e.g.” is a nice reminder that this abbreviation refers to “examples.”

13. Peek or Peak

“Peek” with an “e” means to take a quick glance at something, while “peak” with an “a” means the point or top of something, like a mountain. Check them both out in this sentence:

“Marty loaned me his binoculars for a moment so I could take a quick peek at the mountain peak.”

14. Then or Than

“Then” with an “e” refers to time, while “than” with an “a” is a conjunction used in making comparisons between two things. Check them both out in this sentence:

“I thought about it for a while, then finally decided that I like chocolate better than vanilla.”

15. Compliment vs. Complement

A “compliment” is an expression of praise or admiration, while a “complement” is something that completes something else, or makes it whole. You would “compliment” someone on a great new haircut, perhaps because the haircut “complements” their edgy new style.

An easy way to remember this is that “complement” with an “e” has almost the entire word “complete” in it.

16. Lose vs. Loose

What a difference an “o” makes. To “lose” with one “o” means to be without something. You can “lose” your job, your wallet, your dog, or your mind. “Loose” with two “o’s” refers to the opposite of “tight”—or it may refer to something that isn’t bound together.

Your waistband or your morals might be loose. A key that’s off a chain could be referred to as loose. In fact, if you had a “loose” key, there’s a much greater chance that you might “lose” it.

17. Passive Voice

Passive voice is one of the most common grammar crimes and one of the easiest to correct. Passive voice occurs when the writer turns the object of the sentence into the subject of the sentence, and it instantly weakens the impact of the action. Here’s an example of passive voice:

“A huge bag of chips was eaten by me.”

Here’s the sentence rewritten in an active voice:

“I ate a huge bag of chips.”

See the difference?

18. Continuous vs. Continual

This is a tricky one—two words that sound very similar but have distinctly different meanings. If something is “continuous,” it goes on and on and never stops. If something is “continual,” it is something that happens repeatedly, but may stop for brief periods of time.

If someone was suffering from “continual” coughing, then they’re probably suffering from a cold and have coughing fits throughout the day. If someone is experiencing “continuous” coughing, that would mean that they literally never stop coughing for even a second.

19. Farther vs. Further

Let’s take this argument a little further. See what we did there? We used “further” instead of “farther” because “farther” is only used to refer to physical distance, while “further” is used to describe figurative or metaphorical distance.

You may walk “farther” than ever before, but you would take your relationship with someone a little “further” by moving in with them.

20. Between vs. Among

How do you choose between the words “between” and “among”? Use “between” when you’re choosing between two specific, distinct things. Stick to “among” when you’re talking about a larger, more abstract group of things.

Check out the difference:

“I’m going to choose between the pasta, the steak, and the chicken.”

“I’m going to make a choice from among all of the delicious looking entrees.”

21. Literally

Somehow, over the past decade, “literally” has become one of the most frequently misused words in the English language. “Literally” means “actually, without exaggeration,” but the word is now often used in situations where the writer or speaker is completely exaggerating. It has become a nasty habit for writers and speakers to use “literally” when they actually mean “figuratively.”

“When I saw Janet Jackson in person I literally died.”

If the speaker had literally died, she wouldn’t be speaking in the first place. She would be dead.

22. Lay vs. Lie

OK, this can be hard to remember. Sometimes thinking about it makes us so tired we feel like we need to “lie” down. To “lie” means to recline horizontally, while “lay” means to put something down horizontally. So, you “lie” down in bed, but you “lay” a sweater out on the bed.

Now for the really tricky part—the past tense of “lie” is…”lay.” So, you might actually use “lay” to refer to a person in bed in the past tense. The past tense of “lay,” however, is “laid.” Here are both of the past tenses in one sentence:

“Last night, she laid out her clothes for the next day, then she lay down in bed for the night.”

23. I Could Care Less

This is a grammatical mistake that completely changes the meaning of what the writer is trying to say. When people use the term “I could care less,” they almost always mean “I couldn’t care less.” “I couldn’t care less” means that you don’t care about something at all. “I could care less” means that you care about it a great deal.

Saying “I could care less what people think of my outfit” means that you’re probably actually pretty concerned with other people’s opinion of your clothes. You almost always “could care less” about something. When you say “I couldn’t care less,” that means the opinion of others doesn’t matter.

24. Irregardless

Sometimes less is more. There’s no need to say the same thing twice, especially not within the same word. “Regardless” already means “having no regard for, without concern for.” The prefix “Ir” means “not”—so “irregardless” would actually mean “not having no regard for.” It’s just “regardless.”

25. Principle vs. Principal

Here’s one more trickster from the homonym family that’s been tripping up writers for ages. “Principle” ending in “le” refers to a fundamental belief or rule, while “principal” ending in “al” refers to something or someone at the highest rank of importance—like a principal investment or a high school principal.

So, “principals” probably have some pretty firmly held “principles.” One tip we like to use to keep these straight is thinking about the fact that “principal” ends with the name “Al.” Think of “Al” as the big man in charge—the “principal.”

26. Could of, Would of, Should of

This common error clearly derives from phonetics. The contractions “could’ve,” “would’ve,” and “should’ve” all sound as if they contain the word “of.” In actuality, they’re contractions of the phrases “could have,” “would have,” and “should have.”

27. Dangling modifiers

This grammatical error occurs when an adjective, adverb, or modifying phrase is used in a sentence, but it’s not clear exactly what the writer is modifying.

Here’s an example:

“Confused, the question went unanswered.”

Who is the confused person that the writer is referring to in this sentence? The question itself isn’t confused, but at this point, the reader definitely is. Here’s the corrected sentence without the dangling modifier.

“Confused, the professor chose not to answer the question and just moved on to a different topic.”

If you’re going to leave your readers hanging, do it with the dramatic tension in your brilliant plot twists, not with a dangling modifier.

28. May vs Might

In the “may vs. might” debate, it’s all about the possibilities. Both words refer to something that could possibly happen, but the “might” refers to possibilities that are more remote. You “may” buy a lottery ticket today in the hopes that you “might” win.

“May” implies that it’s a possibility that’s being considered. “I may go out to eat tonight.” “Might” refers to something that is more likely up to fate. “I might get indigestion if I overeat.”

29. Which vs That

This is another troublesome one even for experienced writers. When deciding whether to use “which” or “that,” the easiest thing to do is determine whether the clause that follows “which” or “that” is essential to the sentence, or just descriptive. If it contains non-essential information, use “which.” If the clause is essential to the meaning of the sentence, use “that.”

Check out the difference:

“The apartment, which had two bedrooms, was located on the fourth floor.”

“The apartment that had two bedrooms was located on the fourth floor.”

In the first sentence, the words following “which” merely give more information about the fourth floor apartment. In the second sentence, it’s clear that the writer is identifying a specific apartment. The apartment on the first floor may be a one-bedroom. The apartment on the third floor, perhaps, has three bedrooms. The apartment that has two bedrooms, however, is on the fourth floor.

30. Who vs. That

Welcome to the blurriest line in the world of grammar. For the most part, writers should use “who” to refer to human beings and “that” to refer to inanimate objects. However, using “that” in reference to people is not technically wrong.

That’s right. We’re rounding out the list with something that you’re really not doing wrong at all. It’s always nice to end on a positive note.

Now get out there and get your grammar on! But don’t forget to be engaging, persuasive, and original as well.