10 Common Grammar Mistakes That Will Ruin Your Writing

Everyone makes grammar errors from time to time, but some mistakes are more tricky to identify than others. Even the most seasoned writer will fumble and use “less” instead of “fewer,” or accidentally use the passive voice instead of active.


If you want to improve your overall writing skills, the best way to begin is to learn the rules of grammar. The rules can be difficult to remember, especially if English isn’t your first language. However, once you’re aware of the most common grammar mistakes, it’ll be easier for you to spot them in your own writing and correct them.


There are tons of grammar errors we could cover, but let’s take a look at some of the most common grammar mistakes with some examples.


Source: Pixabay Alt text: magnifying glass looking up grammar in the dictionary


10 Most Common Grammar Mistakes to Look Out For


After going through this list, you may realize you’ve made a few of these mistakes in the past! Not to worry, it’s never too late to learn something new and correct yourself.


1. Subject-Verb Agreement Errors


A mistake a lot of people make when writing is that the subject and the verb don’t match. The verb and subject need to match in number, meaning in singular or plural. If the subject is one person, the verb must agree and reflect that. Here’s an example.


Incorrect: Our dogs is running in the park.


Correct: Our dogs are running in the park.


2. Sentence Fragments


An incomplete sentence is called a sentence fragment. If the sentence is missing an independent clause or a complete verb, it is considered incomplete and is therefore incorrect. The most common way sentence fragments occur is when the meaning of a second sentence is based on a previous sentence. For example:


Incorrect: I don’t like to eat brussel sprouts. Because I dislike the taste.


Correct: I don’t like to eat brussel sprouts because I dislike the taste.


3. Misuse of Contractions and Apostrophes


A lot of people struggle with knowing when to use a contraction or apostrophe. Whether the contraction is “its” vs “it’s,” “your” vs “you’re,” or “they’re” vs “their” vs “there.”


As a rule, anything that uses an apostrophe indicates possession or a contraction. If you can say “it is” or “it has” instead of “it’s” in a sentence and it still makes sense, then you need an apostrophe. Similarly for contractions, if you can say “you are” in a sentence, then you know you should be using “you’re” instead of “your.” Let’s have a look at some examples.


Incorrect: Its cold outside today.


Correct: It’s [it is] cold outside today.


Incorrect: I don’t understand why your mad, their the ones who made a mistake.


Correct: I don’t understand why you’re [you are] mad, they’re [they are] the ones who made a mistake.


4. Passive Voice


It’s common to see a passive voice when the object is put at the beginning of a sentence as opposed to at the end. When the object is at the beginning, then the verb is happening to the object instead of the object causing the verb.


In order to correct this mistake, the sentence needs to be changed to become active. This is a very common mistake, even for experienced writers, and it’s often difficult to pick up on. Here are some examples:


Passive: The baby was held by its mother.


Active: The mother was holding her baby.


Passive: The wall was painted by Jennifer.


Active: Jennifer painted the wall.


Source: Pixabay Alt text: Red pen correcting mistakes on a paper


5. Dangling Modifiers


A dangling modifier is a phrase, clause, or even a word that is separate from the word it’s meant to describe or modify. It makes the sentence sound awkward and can be confusing to read. If your sentence isn’t clear about exactly what is being modified, then chances are there’s a mistake in there.


Incorrect: Checking in his bag, the book was not found.


Correct: Checking in his bag, he didn’t find his book.  



Incorrect: After breaking her leg, it was hard to walk.


Correct: After breaking her leg, Jane found it hard to walk.


6. Comma Splice


When you connect two independent sentences with a comma instead of using a period or a coordinating conjunction, it’s called a comma splice. It’s common for a lot of writers to make the mistake of inserting a comma when using transition words, like however, furthermore, alternatively, etc. Comma splices can sometimes be fixed by using a semicolon but unless you’re a punctuation expert , it’s best to correct it with a period or coordinating conjunction.


Here’s an example:


Incorrect: Jesse was tired, he went to sleep.


Correct: Jesse was tired. He went to sleep.


Also correct: Jesse was tired, so he went to sleep.


7. Run-on Sentences


Another common grammar mistake is using run-on sentences. This happens when two complete sentences are made into one sentence. It can be corrected by using punctuation such as a period, comma, or semicolon and also by using coordinating conjunctions. It’s important to note that just because a sentence is long, doesn’t mean it’s a run-on sentence.


Here’s an example:


Incorrect: My favorite pizza topping is mushrooms they are really tasty I also like pizza with olives.


Correct: My favorite pizza topping is mushrooms because they are really tasty. I also like pizza with olives.


Also correct: My favorite pizza topping is mushrooms; they are really tasty. I also like pizza with olives.


8. Ending a Sentence in a Preposition


A preposition indicates that another word will follow, so when you end a sentence with a preposition, it automatically sounds awkward or unnatural. For example:


Incorrect: Which dress did you decide to go to the party in?


Correct: In which dress did you decide to go to the party?


Some people argue that it’s ok to end a sentence in a preposition in casual writing and in other situations. The rules of grammar can sometimes change with the times, so it’s best to stay on top of the most current accepted rules.


9. Wordiness


As a general rule, don’t use a lot of words to say a little. If you can properly explain something in a few words, there’s no need to inflate your sentence with extra words. It can confuse the meaning of your sentence so the main message isn’t accurately conveyed. This is really common in student essays and assignments when a student is trying to meet a certain word count — however, it’s not a good strategy to use.


Wordy: A little bit of rain falling from the sky is necessary in order for plants and flowers to grow.


Better: A bit of rain is necessary for plants and flowers to grow.


10. Wrong Word Usage


There are tons of commonly misused words that people often get mixed up when writing.  Many of these words are homophones, meaning they sound the same but have different meanings. Some of them have similar meanings but can’t be used interchangeably.


Here are just a few commonly misused words:


  • Accept vs Except: Both words have different meanings but sound similar.


Incorrect: She expected the offer from the university.


Correct: She accepted the offer from the university.


  • Affect vs Effect: Affect is used as a verb, while effect refers to the change itself and is a noun.


Incorrect: The book really effected me.


Correct: The book really affected me.


Also correct: The book had an effect on me.


  • Fewer vs Less: If an item is quantifiable, meaning you’re able to count them, use fewer. When it’s not countable, use less.


Correct: There were fewer students in class than yesterday.


Correct: I drink less water than you do.


  • Number vs Amount: The concept here is the same. Number is used when you can count something, and amount is used when referring to something that can’t be counted.


Correct: The number of shark attacks is increasing.


Correct: There is a large amount of snow outside.


The Bottom Line


While there are dozens of other common grammar mistakes to go over, the ones listed here should give you a good overview of mistakes to stay away from. If you’re a student and you’re worried about your writing skills or you think it can be improved, seek out help from academic advisors.


At University of the People, we have student support advisors who can help you with your writing skills.

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