10 Most Common Grammar Mistakes in English

Woman in a striped shirt and glasses shows regret and places her palm on her forehead

Even native speakers make English grammar mistakes from time to time. Nobody has perfect grammar and with so many rules to remember, you shouldn’t feel bad about making mistakes when speaking or writing English. That said, you should always aim to make as few errors as possible.

One of the best ways to improve your language abilities is by learning how to recognize the most common grammar mistakes in English. Whether you want to write the perfect college entrance essay or sound more professional in your next job interview, there are a few English grammar mistakes that you will want to avoid.

So, let’s take a closer look at the 10 most common grammar mistakes in English writing and speaking.

5 Most Common Grammar Mistakes in English Writing

Though there is some crossover between written and spoken grammar mistakes, some errors are very specific to writing (misspelled words, apostrophe or comma placement, etc).

Even though some of the mistakes below can be made in both formats (writing and speaking), some are more common in one than the other. Here are some of the most common grammar mistakes in English writing:

Their, They’re, or There?

When spoken, the words “there,” “their,” and “they’re” all sound virtually the same. However, they each have very different meanings.

  • Their – “Their” is a possessive pronoun. It signifies ownership of something by one or more people.
    • I visited my grandparents over the weekend. Their house is beautiful.
  • They’re – “They’re” is simply a contraction of “they are.”
    • My friends didn’t bring umbrellas. They’re going to get wet.
  • There – “There” can be an adverb, noun, pronoun, interjection, or adjective. However, it is NOT a possessive pronoun or a contraction.
    • I traveled there during my vacation. (adverb)
    • We can go there or stay here. (noun)
    • There is someone at the door. (pronoun)
    • There, we did it! (interjection)
    • I will always be there for you. (adjective)

You’re vs. Your

Just like the previous example, this one occurs when people confuse two or more words that sound the same. However, “you’re” and “your” mean completely different things.

  • You’re – “You’re” is a contraction of “you are.”
    • I think you’re going to like the movie.
  • Your – “Your” is a possessive pronoun. You should use it for something owned by the person to which you are speaking (or in this case, writing).
    • I forgot to return your pencil.

It’s vs. Its

Are you beginning to see a pattern? When you’re speaking, no one can tell if you’re confusing “it’s” or “its” (as long as the rest of the sentence makes sense). In writing, these common grammar mistakes become much more obvious.

  • It’s – “It’s” is a contraction of “it is.” People often get confused because an apostrophe combined with the letter “S” is usually associated with possession of something (the man’s coat, the woman’s shoe, etc).
    • Have you read this book? It’s one of my favorites.
  • Its – “Its” is a possessive pronoun that signifies ownership by a non-human thing.
    • Look at that tree! Its leaves are so beautiful!

Who’s vs. Whose

While they may sound the same in speech, you can’t mix up “who’s” and “whose” in writing. One is a contraction, while the other is a possessive pronoun.

  • Who’s – “Who’s” is a contraction of “who is.” It cannot be used to refer to the ownership of something.
    • Who’s going to the party tonight?
    • He’s the professor who’s mean to everyone.
  • Whose – “Whose” always signifies ownership of something.
    • Whose pencil is this?
    • She’s the woman whose car was stolen.

Then vs. Than

One of the most common grammar mistakes in writing is the erroneous use of “then” and “than.” Thankfully, the grammar rules for these two are pretty simple.

  • Then – “Then” is always used in relation to time.
    • First I brush my teeth, then I take a shower.
  • Than – “Than” is only used when making comparisons.
    • I weigh less than I did five years ago.

5 Most Common Grammar Mistakes in English Speaking

Now that we’ve covered mistakes people make while writing, it’s time to look at some of the most common grammar mistakes in English speaking. Many native English speakers get lazy when speaking, which often results in incorrect grammar. This makes it all the more confusing for those who are learning to speak English as a second language.

Here are the most common spoken grammar mistakes in English:

Me vs. I

Most intermediate English students know that “I” is the subject pronoun, while “me” is the object pronoun. However, people often mix them up when a sentence includes multiple subjects, multiple objects, or both.

  • Me – “Me” always serves as the object in a sentence. This means that, even when combined with other objects, “me” must always be used as the recipient of the action. An easy way to check if you have it right is to remove the second object and see if it still sounds correct.
    • Kevin threw the ball at my friend and me. *if you remove “my friend,” you’re left with “Kevin threw the ball at me” (CORRECT) as opposed to “Kevin threw the ball at I” (INCORRECT).
  • I – Alternatively, “I” always serves as the subject of a sentence, even if it comes in the second clause. You can use the same trick of removing the second pronoun to see if it still sounds correct.
    • My brother and I went to the movies. *Again, if you remove “my brother,” you’re left with “I went to the movies” (CORRECT), as opposed to “me went to the movies” (INCORRECT).
    • My friends are studious, but no one is more studious than I am.

Who, That, or Which?

When used as pronouns, “who, “that,” and “which” often get mixed up. While “who” is pretty easy to use (as it almost always refers to people), the other two can be a little confusing.

  • Who – “Who” can refer to people and animals.
    • I talked to the man who took my bag.
    • Rufus is the dog who always barks at me.
  • That – “That” can refer to people or animals as well, but it usually refers to groups or multiple things. More importantly, “that” is used to introduce essential clauses (i.e. clauses containing information that is vital to the meaning of the sentence).
    • The woman that works at the library knows me. (Since the word refers to a person, “who” could also be used here)
    • I don’t like to watch movies that last for more than two hours.
  • Which – “Which” can also refer to groups or things. This is why it is often confused with “that.” However, “which” is used to introduce nonessential clauses (i.e. clauses that do not contain information that is vital to the meaning of the sentence).
    • The red car, which almost never starts, finally broke down today.

Less vs. Fewer

Differentiating between countable and uncountable nouns often causes problems for English students. As a result, mixing up “less” and “fewer” is one of the most common mistakes in English speaking. It can help to put nouns with numbers to see if they are countable or uncountable. For example, you can have “three dollars” (countable), but you can’t have “three money” (uncountable).

  • Less – “Less” should only be used when referring to uncountable nouns.
    • I have less money today.
  • Fewer – “Fewer” should only be used with countable nouns.
    • There were fewer people at the meeting.

Who vs. Whom

Many native speakers forego using “whom” in casual conversations entirely, as it can sound somewhat formal. However, if you want to avoid making a grammatical mistake, you have to know when to use both “who” and “whom.”

  • Who – “Who” is a subject pronoun. It can be helpful to replace “who” with another subject pronoun like “he” or “she” to see if it still works for the clause in which it appears.
    • Who is the man? *Test: “he is the man” (CORRECT) vs. “him is the man.” (INCORRECT)
    • He’s the only one who forgot to do his homework. *Test: “He forgot to do his homework” (CORRECT) vs. “him forgot to do his homework.” (INCORRECT)
  • Whom – “Whom” is an object pronoun. You can tell if it is correct by replacing it with another object pronoun like “him” or “her.” However, you may have to rearrange the sentence.
    • He is the man with whom I was speaking. *Test: “I was speaking with him” (CORRECT) vs. “I was speaking with he.” (INCORRECT)
    • Whom do you prefer? *Test: “Do you prefer him/her?” (CORRECT) vs. “Do you prefer he/she?” (INCORRECT)

Look, Watch, or See?

All three of these words refer to actions related to sight, but they each have unique definitions. While they can all be used as action verbs (“look” and “see” can also be nouns), the context in which they are used will vary.

  • Look – “Look” is used to refer to a person or animal moving their eyes in a particular direction.
    • Look over there!
    • What are you looking at?
  • Watch – “Watch” means to look at something for an extended period of time. It also signifies that a person is paying attention to the thing at which they are looking.
    • Did you watch the movie?
    • I like to watch my dogs play.
  • See – “See” refers to a person or animal becoming aware of something using their eyes.
    • It’s cloudy, so you won’t see the moon tonight.
    • I see one rock and two trees.

If you’d like to learn more about common grammar mistakes in English or find a highly qualified English tutor online to help guide you, visit Magoosh Speaking today. Along with tutoring, we also offer our students daily coaching, role play activities to practice your speaking skills, and more interactive content! Visit our appointments page to try an introductory lesson today!