Top 10 Grammar Mistakes Writers Make (And How To Fix Them)

Gary Smailes | 18 November 2025

Agreement and Reference Essentials

Your reader trusts you to keep the grammar invisible. Agreement and reference slip-ups break the spell. They make the line wobble. Tighten these two areas and the prose feels clean and confident.

Subject-verb agreement

Find the true subject. Ignore interrupters. Then pick the verb that matches.

• Prepositional phrases mislead.
  • Wrong: The bouquet of roses are on the table.
  • Right: The bouquet of roses is on the table.
  The subject is bouquet, not roses.
• Collective nouns act as one unit in most U.S. usage.
  • The team is winning.
  • The staff was informed.
  If you want to highlight individuals, name them. The team members are arguing.
• Either, neither, or, and nor follow a proximity rule. The verb agrees with the noun closer to it.
  • Either the manager or the employees are available.
  • Either the employees or the manager is available.
  Read the end of the subject group. Match the verb to that word.
• Indefinite pronouns like each, everyone, and nobody take a singular verb.
  • Each of the runners is tired.
  • Everyone on the committees is present.

Quick tests:

• Swap singular and plural to hear the difference. The team is. The teams are. If your ear twitches, check the subject.
• Cover the prepositional phrase. The list of errors is long. Cover of errors, then read The list is long.

Watch for nearby nouns that pull the verb off course. In The boxes near the sofa was dusty, the subject is boxes, so choose were.

Mini exercise:

• Write three sentences with of phrases. Example starters: A pile of, A box of, A series of.
• Cover the of phrase and choose the verb. Then read the full sentence aloud to confirm the rhythm.

Pronoun problems

A pronoun must match its noun in number and sense. It must point to one clear thing, not a crowd of options. When in doubt, name the noun.

• Ambiguous they
  • Vague: Mia told Ava they missed the deadline.
    Who missed it, Mia or Ava?
  • Clear: Mia told Ava she missed the deadline. If she is Mia, say so.
  • Clearer: Mia told Ava, You missed the deadline.
• Empty it
  • Vague: In the report, it says the road will close.
  • Clear: The report says the road will close.
• Wandering this and that
  • Vague: The committee delayed a vote. This angered the public.
    This refers to what, the delay or the vote?
  • Clear: The delay angered the public.
  Turn this into a determiner when possible. This decision. This delay. This policy.
• Number mismatch
  • Problem: Everyone forgot their ticket, if your house style rejects singular they.
  • Options:
    • Use singular they if your style allows it. Everyone forgot their ticket.
    • Make the noun plural. All attendees forgot their tickets.
    • Rebuild the sentence. Every attendee forgot a ticket.
• Gender and pronoun choice
  Respect stated pronouns for named people. For a generic person, singular they is standard in many guides. Pick a house rule and stay consistent across the manuscript.

The replace test:

• Find each pronoun. Replace it with each possible noun nearby.
• If more than one noun fits, the reference is fuzzy.
• If the verb form shifts after replacement, the number does not match.

Example:

• Original: When Lena texted Maya about the photos, she ignored it.
• Replace she with Lena or Maya. Both fit. Replace it with photos. The verb ignored does not match photos in sense. Rewrite:
  • When Lena texted Maya about the photos, Maya ignored the message.
  • When Lena texted Maya about the photos, Lena ignored the reply.

Pick the meaning you intend, then state it.

Long sentences invite pronoun trouble. Break a chain into two lines if the reference begins to blur.

Checklist for every page:

• Circle they, it, this, that, which, who. Ask, does each one point to a single, clear noun?
• Check number. Singular subject, singular verb, matching pronoun.
• Read aloud. If you hesitate before a pronoun, the reader will too.

A few quick fixes in the wild:

• Vague: The lab sent results to Dr. Ortiz and Dr. Shaw, and she will call tomorrow.
• Clear: The lab sent results to Dr. Ortiz and Dr. Shaw. Dr. Ortiz will call tomorrow.

• Vague: The novel mentions a map in chapter one, but it never appears again.
• Clear: The novel mentions a map in chapter one, but the map never appears again.
• Better: The novel mentions a map in chapter one, then forgets it.

Final habit:

When you finish a scene, run a find for of, either, neither, everyone, team, staff, they, it, this, that. Then test each line. Small adjustments here save reader trust later.

Sentence Structure and Modifier Pitfalls

Tangled sentences slow your reader and hide your point. Clean structure is not fancy. It is a set of simple habits that keep ideas in order and modifiers in their place.

Run-ons and comma splices

A run-on shoves two complete sentences together with nothing in between. A comma splice uses a comma where a stronger join is needed. Both look harmless on the page. Both make your prose feel loose.

Test for independence. If the words on each side of the comma stand as full sentences, you need a stronger link.

• Comma splice:
  • Wrong: The sun dipped below the hills, the town exhaled.
  • Right: The sun dipped below the hills. The town exhaled.
  • Also right: The sun dipped below the hills, and the town exhaled.
• Fused run-on:
  • Wrong: He saved the file he lost it anyway.
  • Right: He saved the file, but he lost it anyway.
  • Also right: He saved the file. He lost it anyway.

Use one of three repairs.

• Period. Clean, decisive. Two sentences, two beats.
• A comma plus a coordinating conjunction. For, and, nor, but, or, yet, so. Pick the one that shows the relationship.
• A semicolon. Good for tight links between two independent clauses. Name it in your style guide, then use it with restraint.

A fourth option, subordination, tightens the logic.

• Before: The report was late, the team stayed to finish it.
• After: The team stayed to finish the report because it was late.
• Or: Because the report was late, the team stayed to finish it.

Read the line aloud. Mark where your voice wants a stop. If the pause sounds like the end of a thought, give the reader a period. If the second part leans on the first, link them with a conjunction.

Common traps:

• Transitional adverbs are not conjunctions.
  • Wrong: The plan failed, however we learned a lot.
  • Right: The plan failed. However, we learned a lot.
  • Also right: The plan failed, but we learned a lot.
• Overlong lists of actions with commas doing all the work.
  • Muddy: She opened the door, stepped outside, the cat ran past her, she called its name.
  • Clear: She opened the door and stepped outside. The cat ran past her. She called its name.

Quick exercise:

• Write three comma splices about your morning. Example: I made coffee, the kettle screamed.
• Fix each one three ways. One with a period. One with a conjunction. One with subordination.

Dangling and misplaced modifiers

A modifier belongs next to the word it describes. When it floats, it dangles. When it drifts across a line, it points at the wrong thing. Either way, your sentence says something you did not mean.

Ask one quick question for every opener or phrase. Who or what is doing the action?

• Classic dangle:
  • Wrong: Walking to the store, the rain soaked me.
  The phrase Walking to the store describes you, but the sentence points it at the rain.
  • Right: Walking to the store, I was soaked by the rain.
  • Better: As I walked to the store, the rain soaked me.
• Hidden subject:
  • Wrong: After reviewing the dataset, the errors were obvious.
  Who reviewed the dataset? The sentence says the errors did.
  • Right: After reviewing the dataset, I found the errors obvious.
  • Also right: The errors were obvious after I reviewed the dataset.
• Misplaced only and almost:
  • Shifted meaning: She only ate vegetables on Mondays.
  Does she eat them only, or only on Mondays?
  • Clear intent: She ate only vegetables on Mondays.
  • Different meaning: She ate vegetables only on Mondays.
• Squinting modifier, stuck between two targets:
  • Unclear: Students who study often improve grades.
  Does often modify study or improve?
  • Clear one: Students who often study improve grades.
  • Clear two: Students who study improve grades often.
• Long distance modifier:
  • Wrong: He served soup to the guests in bowls.
  Were the guests in bowls?
  • Right: He served soup in bowls to the guests.
• Which vs. what it modifies:
  • Muddy: She mailed a package to her sister which was wrapped in blue paper.
  Which refers to sister or package?
  • Clear: She mailed a package, which was wrapped in blue paper, to her sister.
  • Or: She mailed her sister a package wrapped in blue paper.

Keep modifiers close to their targets. In most cases, place a descriptive phrase right before or right after the noun it describes. When you use an introductory phrase, make sure the subject that follows is the one doing the action in that phrase.

A fast line edit trick:

• Circle every opener, like After dinner, While driving, or Hoping for a raise.
• Draw an arrow to the subject of the main clause.
• If the subject is not the actor in the opener, revise.

Another quick test:

• Read the sentence with the modifier removed. Does the core still make sense? Then rebuild the sentence with the modifier snug against its noun or verb.

Mini exercise:

• Fix these, then write one of your own.
  • Running across the yard, the gate swung open.
  • Nearly fed, the baby cried for another bottle.
  • He promised to call her often who lives in Boston.

Possible fixes:

• Running across the yard, I swung the gate open.
• Nearly fed, the baby still cried for another bottle. Or better, The baby, nearly fed, still cried for another bottle.
• He

Punctuation That Changes Meaning

Tiny marks, big consequences. A comma or apostrophe can sharpen a sentence or wreck it. Use them on purpose, not on instinct.

Commas that help, commas that hurt

Start with an easy check. If you can lift a phrase out and the sentence still holds its core meaning, set that phrase off with commas.

• Nonrestrictive clause:
  • Wrong: My brother who lives in Denver teaches math.
  • Right if you have one brother: My brother, who lives in Denver, teaches math.
  • Right if you have many brothers and mean one specific brother: My brother who lives in Denver teaches math.
• Appositives:
  • Wrong: My wife Sarah is on call.
  If you have one wife, the name is extra info and needs commas.
  • Right: My wife, Sarah, is on call.
  • Different meaning: My wife Sarah is on call suggests you have more than one wife.
• Introductory elements:
  • Wrong: After dinner we walked to the river.
  • Right: After dinner, we walked to the river.
  • Wrong: In the morning I will email you.
  • Right: In the morning, I will email you.
• Overuse in simple sentences:
  • Choppy: She opened her laptop, and started the call.
  • Smooth: She opened her laptop and started the call.
  One subject, two verbs, no comma needed.
• Transitional words need commas:
  • Wrong: Yes we can meet at two.
  • Right: Yes, we can meet at two.
  • Wrong: Unfortunately the file is missing.
  • Right: Unfortunately, the file is missing.

Now the serial, or Oxford, comma. Use it in lists of three or more. It prevents confusion.

• Without the Oxford comma:
  • We spoke to the lawyers, Alice and Ben.
  Are Alice and Ben the lawyers, or three parties total?
• With the Oxford comma:
  • We spoke to the lawyers, Alice, and Ben.
  Clear list of three.

Another test. If a sentence with a middle clause sounds like a sidebar when read aloud, give it commas on both sides. If the clause names which one, not extra info, leave the commas out.

Quick practice. Fix these.

• Before leaving we checked the locks.
• The report which was updated yesterday is final.
• My colleague Dana is presenting, and will send slides.

Possible fixes:

• Before leaving, we checked the locks.
• The report that was updated yesterday is final. Or, The report, which was updated yesterday, is final, if the update is extra info.
• My colleague Dana is presenting and will send slides.

Check your choices with a trusted guide. CMOS is clear on these rules and gives edge cases when your ear is not enough.

Apostrophes, possessives, and plurals

Use apostrophes for ownership and for missing letters in contractions. Not for plain plurals.

• Its and it's:
  • it's means it is or it has. Test by replacing it with it is.
  • its shows possession.
  • Right: It's late. The dog lost its collar.
• Singular possessive:
  • Add 's to a singular noun.
  • The editor's note. The bus's route. James's draft.
  CMOS favors 's even when the word ends in s. Some houses choose James' in-house. Pick a style and stay consistent.
• Regular plural possessive:
  • Make the plural, then add an apostrophe.
  • The neighbors' house. The teachers' lounge. The cars' engines.
• Irregular plural possessive:
  • If the plural does not end in s, add 's.
  • The children's books. The men's team. The people's choice.
• Shared vs separate possession:
  • One thing owned together: Sam and Maya's car.
  • Two things owned separately: Sam's and Maya's cars.
• Compound words:
  • The mother-in-law's coat. The editor in chief's decision.
• Pronouns already carry possession without apostrophes:
  • hers, yours, theirs, ours, whose. No apostrophes there.
  • Wrong: The team lost they're focus.
  • Right: The team lost their focus.
• Plain plurals do not take apostrophes:
  • 1990s, not 1990's.
  • FAQs, URLs, CEOs.
  • Dos and don'ts looks odd, but that is the standard.
• Contractions need apostrophes where letters drop:
  • you're for you are, don't for do not, we've for we have.
  • Test by expanding the phrase.

When you are stuck, try the of test. If you can rephrase as the X of Y, you likely need a possessive. The cover of the book is the book's cover. If the of test sounds wrong, you might want a simple plural. Three pizza's is never right unless something belongs to a pizza.

Mini exercise. Fix these.

• The company's grew fast in the 2000's.
• James' essay lost it's last page.
• The womens team forgot there jerseys.
• I met my editors assistant and reviewed the authors notes.

Possible fixes:

• The companies grew fast in the 2000s.
• James's essay lost its last page.
• The women's team forgot their jerseys.
• I met my editor's assistant and reviewed the author's notes.

One last habit. When you line edit, search for apostrophes. Check every one. Then search for its and it's, your and you're, their

Timeline and Balance Issues

Time and rhythm create the backbone of clear prose. When you slip between tenses or build lopsided lists, readers stumble. Fix these problems and your writing flows.

Tense shifts that confuse readers

Pick a tense. Stick with it. Sounds simple, but writers drift between past and present without noticing.

Here's the problem in action:

• Messy: Sarah walked to the corner store. The clerk looks up and smiles. She buys milk and heads home.
• Clean: Sarah walked to the corner store. The clerk looked up and smiled. She bought milk and headed home.

Choose past or present for your main narrative. Most fiction uses simple past. Present tense works for immediacy but requires more discipline.

Once you choose, hold that line within scenes. You break the tense only for good reasons:

• Past perfect for actions that happened before your main timeline:
  • Right: Maria opened the letter Tom had written three days earlier.
  • Wrong: Maria opened the letter Tom wrote three days earlier.
  The past perfect "had written" shows the writing came first.
• Present tense for universal truths or ongoing conditions:
  • Right: He remembered that water boils at 100 degrees Celsius.
  • Right: She knew her mother loves surprises.
• Future constructions when characters plan ahead:
  • Right: Tom said he would call tomorrow.

Watch for these common drift patterns:

Starting in past, sliding to present:

• Wrong: The meeting began at nine. Everyone arrives on time except Janet.
• Right: The meeting began at nine. Everyone arrived on time except Janet.

Mixing tenses in dialogue tags:

• Wrong: "I'm ready," she said and walks to the door.
• Right: "I'm ready," she said and walked to the door.

Historical present creeping in:

• Wrong: The author was born in 1950. She writes her first novel at age thirty.
• Right: The author was born in 1950. She wrote her first novel at age thirty.

Here's a quick test. Search your draft for "was," "were," and "had." If you started in past tense, these words should dominate. A sudden cluster of present-tense verbs signals a drift.

Another check: read dialogue and tags aloud. Your ear will catch mismatched tenses faster than your eyes.

Past perfect needs strategy. Use it to set up backstory, then return to simple past:

• Clunky: She had eaten breakfast, had brushed her teeth, and had left for work.
• Smooth: She had eaten breakfast and brushed her teeth before leaving for work.

Set the earlier timeline with "had," then drop it. Readers understand the sequence.

Present tense demands consistency:

• Wrong: She walks to the window and looked outside.
• Right: She walks to the window and looks outside.

Present tense feels natural in first person but gets tricky with flashbacks. Handle them with care:

• Right: I remember the day when my father taught me to drive.

Past events stay in past, even in present-tense narratives.

Parallelism that creates rhythm

Lists and comparisons need matching forms. When structures align, sentences sing. When they clash, readers trip.

Basic parallelism in lists:

• Wrong: She likes hiking, swimming, and to read books.
• Right: She likes hiking, swimming, and reading books.
• Right: She likes to hike, to swim, and to read books.

Parallel verb forms:

• Wrong: The manager will review applications, interview candidates, and making final decisions.
• Right: The manager will review applications, interview candidates, and make final decisions.

Parallel adjectives:

• Wrong: The report was thorough, detailed, and it was comprehensive.
• Right: The report was thorough, detailed, and comprehensive.

Parallel phrases:

• Wrong: We need someone who writes well, speaks clearly, and with leadership skills.
• Right: We need someone who writes well, speaks clearly, and leads effectively.
• Right: We need someone with strong writing, clear speaking, and effective leadership.

Correlative conjunctions demand balance. Pairs like "not only...but also" and "either...or" need matching structures:

• Wrong: She not only studied hard but also was working late.
• Right: She not only studied hard but also worked late.

• Wrong: Either we leave now or staying until morning.
• Right: Either we leave now or we stay until morning.
• Right: We either leave now or stay until morning.

Comparisons need parallel elements:

• Wrong: Running marathons is harder than to swim laps.
• Right: Running marathons is harder than swimming laps.

• Wrong: I prefer writing by hand more than using a keyboard.
• Right: I prefer writing by hand to using a keyboard.
• Right: I prefer writing by hand more than typing.

Read lists aloud. Your ear catches rhythm problems faster than your brain. If you stumble over a list, the structure needs work.

Practice with these broken examples:

• The course covers research methods, how to write clearly, and statistical analysis.
• Not only did she finish the project early, but she also was helping her teammates.
• Swimming is more relaxing than to run.

Better versions:

• The course covers research methods, clear writing, and statistical analysis.
• Not only did she finish the project early, but she also helped her teammates.
• Swimming is more relaxing than running.

Watch for hidden parallelism. Sometimes balance problems hide in longer sentences:

• Wrong: The new system saves time, reduces errors, and employees find it easy to use.
• Right: The new system saves time, reduces errors, and is easy for employees to use.

Parallelism applies to larger structures too. If you start paragraphs with similar topics, keep the sentence structures similar:

• Weak: First, the budget needs review. Second, we should consider staff changes. The timeline is also important to discuss.
• Strong: First, we need to review the budget. Second, we

Word Choice, Dialogue, and Consistency

The devil lives in the details. Small word choices and punctuation marks separate polished prose from amateur hour. Master these fundamentals and your writing gains instant credibility.

Commonly confused words that trip up writers

Every writer has blind spots. Words that sound similar but mean different things. Words that follow different rules depending on context. The solution: know your weakness and hunt it down.

Affect versus effect causes more grief than any other word pair. Here's the simple fix:

• Affect = verb (to influence): The rain will affect our picnic plans.
• Effect = noun (result): The rain had a negative effect on our picnic.

Memory trick: Affect = Action (verb). Effect = End result (noun).

The confusion comes from rare exceptions. "Effect" becomes a verb when you mean "to cause" (The new CEO hopes to effect change). "Affect" becomes a noun in psychology (The patient showed flat affect). Ignore these exceptions unless you write academic papers.

Lie versus lay stumps even experienced writers because the forms overlap:

Present tense:

• Lie = rest flat: I lie down for a nap.
• Lay = put something down: I lay the book on the table.

Past tense gets tricky:

• Lie becomes lay: Yesterday I lay down for a nap.
• Lay becomes laid: Yesterday I laid the book on the table.

Past participle:

• Lie becomes lain: I have lain here for an hour.
• Lay becomes laid: I have laid three books on the table.

Memory trick: Lay needs an object. You lay something down. You lie down yourself.

Who versus whom follows subject versus object rules:

• Who = subject (does the action): Who wrote this letter?
• Whom = object (receives the action): To whom did you give the letter?

Quick test: Replace with he/him. If "he" sounds right, use "who." If "him" sounds right, use "whom."

• Who/He wrote the letter? (Who is correct)
• You gave the letter to whom/him? (Whom is correct)

Modern trend: "whom" is dying except in formal writing. "Who did you see?" sounds natural now, even though "whom" is technically correct.

Fewer versus less depends on countability:

• Fewer = countable things: fewer books, fewer people, fewer mistakes
• Less = uncountable things: less water, less time, less effort

The grocery store sign "10 items or less" drives grammar fans wild. Should be "10 items or fewer" because you count items.

Gray area: less with numbers that represent units (less than $50, less than three miles). Both work here.

Then versus than sounds obvious but gets switched in fast typing:

• Then = time sequence: First we eat, then we leave.
• Than = comparison: She's taller than her brother.

Build your personal hit list. Track the words you mix up. Everyone has different blind spots. Your list might include:

• Principal (main) versus principle (rule)
• Complement (complete) versus compliment (praise)
• Discrete (separate) versus discreet (careful)
• Stationary (still) versus stationery (paper)

Create a simple style sheet. Write the correct usage for each word pair. Keep it handy during editing.

Use targeted searches. When you finish a draft, search for your problem words. Find every instance and check the usage. This catches mistakes your eye misses.

Dialogue punctuation that looks professional

Dialogue reveals amateur writing faster than anything else. Get the punctuation wrong and readers notice immediately. The rules are simple once you learn them.

Punctuation goes inside quotation marks:

• Right: "I'm ready," she said.
• Wrong: "I'm ready", she said.

• Right: "Are you coming?" he asked.
• Wrong: "Are you coming"? he asked.

This applies to American English. British English sometimes puts punctuation outside, but pick one system and stick with it.

Comma before dialogue tags with speaking verbs:

• Right: "The meeting starts at noon," Tom said.
• Right: "Where are you going?" she asked.
• Right: "Stop right there!" he shouted.

Notice the comma after "noon" and the question mark/exclamation point after "going" and "there." The punctuation changes based on the sentence type, but it always goes inside the quotes.

Period before action beats:

Action beats are not dialogue tags. They describe physical actions, not ways of speaking.

• Right: "I'm leaving." She grabbed her coat and headed for the door.
• Wrong: "I'm leaving," she grabbed her coat and headed for the door.

• Right: "The answer is no." He slammed the book shut.
• Wrong: "The answer is no," he slammed the book shut.

Capitalize dialogue tags correctly:

• Right: "Hello there," she said. (lowercase "she")
• Right: "Hello there." She waved her hand. (uppercase "She")

The first example continues the same sentence. The second example starts a new sentence.

No comma after dialogue ending with question mark or exclamation point:

• Right: "Where are you going?" she asked.
• Wrong: "Where are you going?," she asked.

• Right: "Look out!" he yelled.
• Wrong: "Look out!," he yelled.

Handle interrupted dialogue carefully:

• Right: "I think," Tom said, "we should leave early."
• Right: "I think we should go." Tom stood up. "The weather is getting worse."

In the first example, the dialogue is one sentence split by the tag. In the second example, they're separate sentences.

Watch capitalization in split dialogue:

• Right: "I believe," she said, "this is the right choice." (lowercase "this")
• Right: "I'm not sure." She paused. "Maybe we should wait." (uppercase "Maybe")

If the dialogue would be one sentence without the tag, keep the second part lowercase. If they're separate sentences, capitalize the second part.

Frequently Asked Questions

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