This guide takes the guesswork out of grammar, punctuation, and style for your college essays. We'll walk through the most common mistakes students make—and show you exactly how to fix them.

17 Common Grammar & Style Mistakes

1. Dangling/Misplaced Modifiers

A modifier is a word, phrase, or clause that adds detail to another part of your sentence. When modifiers wander too far from what they're describing—or when it's unclear what they're describing at all—your reader ends up confused.

Dangling modifiers leave readers guessing. The modifier doesn't clearly attach to the right noun.

Examples:

Incorrect: Running late for the interview, the elevator seemed impossibly slow. (The elevator wasn't running late—you were.)
Incorrect: After studying all night, the exam still felt impossible. (The exam didn't study; the student did.)
Correct: After studying all night, Maya still found the exam impossible.

Misplaced modifiers technically attach to something—just the wrong thing.

Examples:

Incorrect: I saw a dog walking to class that was barking loudly. (Your class was barking?)
Correct: Walking to class, I saw a dog that was barking loudly.

2. Absolutes/Extreme Language

Words like "always," "never," "all," "none," "everyone," and "no one" rarely hold up under scrutiny. Admissions readers know that life isn't that black-and-white—and sweeping claims can make your essay feel exaggerated rather than authentic.

Examples:

Incorrect: I have never backed down from a challenge in my life.
Correct: I've learned to face challenges head-on, even when they intimidate me.
Incorrect: Everyone at my school participates in community service.
Correct: Most students at my school participate in community service.

3. Subject/Verb Agreement

Your subject and verb need to match—singular with singular, plural with plural. Simple enough, except English loves to throw curveballs. Here's how to handle the tricky cases:

Subjects joined by "and" take a plural verb.

My mentor and my coach have shaped who I am today.
The debate team and the Model UN club meet on the same night.

Singular nouns joined by "or" or "nor" take a singular verb.

Either the counselor or the principal signs the form.
Neither the library nor the coffee shop stays open past 9 p.m.

When "or" or "nor" joins singular and plural nouns, match the verb to whichever noun is closest.

Either the seniors or the junior is presenting first.
Either the junior or the seniors are presenting first.

Ignore phrases that come between the subject and verb—the verb still agrees with the subject.

The stack of applications on my desk grows taller every day.
A portfolio of creative writing samples is required.
The dorm, along with both adjacent buildings, was built in the 1960s.

Collective nouns ("team," "committee," "family") act as a single unit and take singular verbs.

The admissions committee reviews applications in rounds.
My robotics team is competing at nationals this year.
A flock of geese has taken over the campus quad.

Words that look plural but aren't—like "news," "physics," "economics," and "politics"—take singular verbs.

Physics was my hardest class junior year.
The news from the financial aid office is encouraging.

Paired nouns like "scissors," "glasses," and "jeans" take plural verbs.

These glasses are scratched beyond repair.
My lucky interview pants were at the dry cleaner.

Indefinite pronouns like "each," "everyone," "someone," and "no one" take singular verbs.

Everyone on the waitlist hopes for good news.
No one in my family has attended a four-year college.
Each of the essays requires a different approach.

4. Oxford Comma

The Oxford comma (also called the serial comma) is that final comma before "and" in a list. People have strong feelings about this tiny punctuation mark. We're firmly Team Oxford Comma—here's why:

It prevents ambiguity. Consider: I admire my parents, Oprah and Elon Musk. Without the Oxford comma, it sounds like your parents are two very famous people. Add the comma—my parents, Oprah, and Elon Musk—and the meaning is clear.

Academics expect it. The people reading your essays likely use it themselves. In fact, one missing Oxford comma cost Maine dairy companies $5 million in a lawsuit over overtime pay. The stakes in your essay aren't quite that high, but clarity always matters.

Bottom line: When in doubt, include the comma.

Examples:

My extracurriculars include debate, volunteer tutoring**,** and varsity tennis.
The research project required gathering data, analyzing results**,** and presenting findings to the faculty.

5. Em-Dash vs. En-Dash

Em dashes are often used similarly to commas, parentheses, or colons—though it's important to keep in mind that em dashes will have a slightly different effect for a reader than each of those other punctuation marks. En dashes are generally used to indicate things like a range of numbers or connections between things (e.g., east-west railroad).

Examples:

The em-dash**—so named because it's the width of the letter m—**is the longest dash.
The en-dash – so named because (you guessed it) it's the width of the skinnier letter n – is the shorter of the two.

Notice in these examples, the em-dash has no spaces around it, while the en-dash does. We have a slight preference for using the em-dash, without spaces. Why? It's cleaner and uses fewer characters (the em-dash counts as one character, while the en-dash counts as three, since it has spaces on either side).

Note: Be sure to be consistent with spacing when using these dashes throughout the essay.

6. Hyphens

Knowing when to use a hyphen, and when to leave it out, can be confusing. Below are some basic rules to remember.

Hyphenate two-word adjectives before a noun, but don't hyphenate if they come after the noun.

The world-class design won many awards.
The design was world class, winning many awards.
She wanted to live in off-campus housing.
Her dorm was off campus.

Hyphenate compound numbers, no matter where they are in a sentence.

The teacher had a party in her classroom when she turned fifty-six.
The Smiths have a 10-year-old.

Use a hyphen with the prefixes ex-, self-, and all-.

He was a self-described genius.
He was an ex-military officer.
The class was all-inclusive.

Use a hyphen with the suffix -elect.

The president-elect will be inaugurated in January.
The mayor-elect gave a speech.

Use a hyphen with a prefix that comes before a number, a capitalized word, or a vowel.

The revolt occurred in the mid-1900s.
The pre-Civil War era is also considered the Antebellum Period.
Federal authorities believe anti-aircraft missiles took the plane down.

7. Quotation Marks

With quotation marks, the most common mistakes are made in how they are used. Below are the two rules people often forget.

Punctuation goes inside quotation marks.

"I love it when my teacher gives extra credit," Sally said. "It helps me stress less about getting every answer right."
He was told to "stand his ground."
Rebecca didn't know what her teacher meant when she said to "do the right thing," asking for specific examples.

Exception: When the question mark isn't part of the quote, as in: Why would anyone say, "It is what it is"?

Use double quotes for quotation marks. Some people mistakenly use the single quote mark (') for quotes, but that mark is almost always used instead as an apostrophe.

Exception: Use single quotes to set off a quote within a quote, as in: "John keeps saying, 'Don't do that,' when I twirl my hair," Jackie said.

8. Parallel Structure

Parallel structure, also called parallelism, refers to using the same form or phrase type in writing. For example, if you're using a gerund (a noun derived from an -ing conjugation of a verb) in one phrase, use gerunds in all to match.

Examples:

Do this: The camp offered fishing, boating and kayaking on weekends in the summer.
Not this: The camp offered fishing, boating and rides in a kayak on weekends.
Do this: The professor instructed the students to take out their pencils, write down what they think will be on the test, and turn their papers in.
Or also: The professor instructed the students to take out their pencils, to write down what they think will be on the test, and to turn their papers in.
Do this: The class had several main goals: to teach the basics of physics, to prepare students for advanced physics, and to get students used to working in teams.
Or also: The class had several main goals: teaching the basics of physics, preparing students for advanced physics, and getting students used to working in teams.
Not this: The class had several main goals: to teach the basics of physics, preparing students for advanced physics, and students learn how to work in teams.

9. Spacing at the End of a Sentence

The double space after periods originated in the bygone days of typewriters, when a practice called monospace typesetting reigned. But in the decades since the writing public switched to computers and their easy-to-read font styles, the extra space has not only become unnecessary; many typographers argue that the large gaps between sentences make the written word harder to read.

Essay writers like you have another reason to drop the extra space: It uses up precious characters in essays with strict limits. So, conserve your resources: Save the space.

10. Exclamation Marks

They are used to add emphasis, but in many professional writings, including college essays, exclamation marks tend to make you look like you're trying too hard. Instead of relying on a single punctuation mark, use word choice to convey your emotion.

Exceptions: As the cliché goes, there are exceptions to every rule, and the exclamation point is no exception. Below are examples of when the exclamation mark is more acceptable:

In direct quotes that express emotion: She looked at me hard and snapped, "I can't believe you even said that!"
When using onomatopoeia: I turned around, and, bam! The door slammed in my face.

11. Ambiguous Pronouns

One way that pronouns (it, he, she, they, etc.) are useful is in helping us avoid repetition. They allow us to refer back to a noun without having to mention it again by name. An ambiguous pronoun causes confusion when it's not clear which noun it's referencing—especially when the same pronoun could be used with either noun.

Examples:

Incorrect: Julie took Sandy to the movies after she got home from work. (Who is "she"?)
Correct: After Julie got home from work, she took Sandy to the movies.
Incorrect: When the vase toppled onto the glass shelf, it broke. (What broke—the vase or the shelf?)
Correct: The vase broke when it toppled onto the glass shelf.

12. Formatting Do's & Don'ts

All Caps

Don't use all caps to emphasize words—it SEEMS LIKE SHOUTING. Use italics sparingly instead.
Do use all caps for acronyms, but spell out the full name first: The Centers for Disease Control and Prevention (CDC) issued a statement. The CDC recommends...

Capitalization

Course names: Capitalize them — Intro to Biology, Advanced Calculus
Job titles: Capitalize when used with a name, lowercase otherwise — President Lincoln but the president gave a speech
"High school": Don't capitalize unless it's part of a specific name — I attended Lincoln High School but my high school doesn't offer AP classes
Publications: Include "The" if it's part of the name — The New York Times

Italics

Use italics for:

Emphasis (sparingly—once per essay max): Did you really mean that?
Foreign words: My abuela made tamales.
Internal dialogue: This is it, I thought. Now or never.
Titles of standalone works: books, films, TV shows, newspapers, albums — The Great Gatsby, Stranger Things, The New York Times

Quotation Marks

Use quotation marks for:

Titles of smaller works (chapters, articles, episodes, songs): "The One Where They Graduate" from Friends
Direct quotes: "The only thing we have to fear is fear itself."

Pro tip: Save direct quotes for statements with personality or emotion. Paraphrase routine facts instead of quoting them.

13. Incomplete Comparisons

An incomplete comparison describes one element in a comparative sense (better, worse, stronger, tastier) without naming the second element. The easy fix is to simply add the second element.

Examples:

Do this: The meal was healthier and tastier than the students expected of a lunchroom.
Not this: The meal was healthier and tastier. (Than what?)
Do this: The 2020 Chevy Impala is sleeker and more aerodynamic than earlier models.
Not this: The 2020 Chevy Impala is sleeker and more aerodynamic. (Than what?)

14. Numbers

Different style guides have different rules. Pick one approach and stay consistent throughout your essay.

The simple rule (AP Style): Spell out one through nine; use numerals for 10 and above.

Three students but 15 students
Always use numerals for ages, times, measurements, and percentages: 6 feet tall, 3 p.m., 25%

The academic rule (MLA Style): Spell out numbers you can write in one or two words.

Twelve, thirty-five, one hundred — but use numerals for 102 or 1,054

Universal rules:

Never start a sentence with a numeral. Rewrite or spell it out: Thirty people attended (not 30 people attended)
No apostrophes in decades: the 1990s (not the 1990's)

15. Overused Words

Many of the choices you'll make in writing your college essays will involve what to put in—facts, details, color, anecdotes, even specific words. But when it comes to deciding which words will help you make an impact, you may also consider leaving a select few out, because they are often overused, in college essays specifically. Below is a list of common words we'd recommend replacing with stronger, less common synonyms, if possible.

Most commonly overused:

Passion
Important, crucial, etc., unless it's followed by an explanation about why or how something is important
Interesting/interested in, unless it's followed by an explanation about why or how something is interesting
Expletive constructions ("it was," "it is," "there was," "there is"—basically, an unclear pronoun plus a "to be" or "to have" verb), unless trying to emphasize info that follows (as in: It was clear—she didn't know what she was doing.)
"That" as a subordinating conjunction or following bridge verbs (as in: He knew that he was going to do well on the test.). Removing "that" in these instances is also a quick and easy way to trim excess words.
Very
Really

Somewhat overused:

Myriad
Plethora
Literally
Real-life and hands-on (especially in essays by engineering students)
"Satiate my curiosity" (as in: "Brown's PMLE program offers educational opportunities that will allow me to satiate my curiosity about how the body works.")

16. Passive Voice

To be clear, passive voice is not a grammatical error—there are even (somewhat rare) instances in which passive voice is a stronger choice than active voice. But as a general guideline, writing in passive voice tends to dilute the message and diminish the effectiveness of what you're trying to communicate. So, generally stick with active voice to speak clearly and concisely, using action verbs and clear sentence construction to deliver strong, coherent thoughts.

Examples:

Passive voice: The cookie jar was smashed by Jenny.
Active voice: Jenny smashed the cookie jar.
Passive voice: Our morals and standards are driven by integrity.
Active voice: Integrity drives our morals and standards.

For anyone who's curious, passive voice is primarily a verb construction in which the verb contains a form of [to be] + past participle, like "was smashed" or "are driven" in the example above. (Passive voice is often defined as "when a thing isn't doing the thing that it's doing in a sentence"... but that doesn't seem super useful or clear.)

And if you really want to dig into it, in particular to see instances in which passive voice is a good choice, UNC Chapel Hill does so nicely here.

17. Punctuation

Apostrophes

Possessives: Apostrophe before s for singular (the girl's mother), after s for plural (the girls' team)
Decades: No apostrophe — the 1990s, not the 1990's

Colons

Use colons to introduce a list or emphasize what follows. Capitalize after a colon only if it's a full sentence.

He knew what he had to do: run.
I'll tell you this: Punctuation is tricky. (Full sentence, capitalized)
The dog knew how to beg: with his eyes. (Fragment, lowercase)

Commas

Where you need them:

After introductory clauses: After the interview, I felt relieved.
Around parenthetical phrases: The book, which I borrowed last week, was excellent.
Before conjunctions in compound sentences: I studied hard, and I passed.
When addressing someone: Let's eat, Grandma. (Very different from Let's eat Grandma.)

Where you don't:

After question/exclamation marks in quotes: "Really?" she asked. (not "Really?," she asked.)
Between subject and verb: The team is ready. (not The team, is ready.)
After "but" or "yet" at the start: But he was wrong. (not But, he was wrong.)
In "not only...but also": He was not only smart but also kind.

Comma splices — a common error. Don't join two complete sentences with just a comma:

Wrong: He loved the class**,** he signed up again.
Right: He loved the class**,** so he signed up again. / He loved the class**;** he signed up again. / He loved the class**.** He signed up again.

Semicolons

Join related independent clauses: She finished early; he was still working.
Separate list items that contain commas: I've lived in Austin, Texas; Portland, Oregon; and Miami, Florida.
Before conjunctive adverbs: It was raining; however, we went anyway.

That's all for now. Have an issue that isn't covered here? Google it! Now go forth with grammar and style.