Common Grammar Mistakes in Academic Writing (And How to Avoid Them)

Even experienced writers make grammar errors. Understanding the most common mistakes helps you catch them in your own work.

Subject-Verb Agreement

The Rule

Subjects and verbs must agree in number.

Common Mistakes

Separated Subject and Verb:
❌ "The analysis of the results show significant trends."
✓ "The analysis of the results shows significant trends."

Collective Nouns:
❌ "The team are presenting their findings."
✓ "The team is presenting its findings." (American English)
✓ "The team are presenting their findings." (British English)

Neither/Either:
❌ "Neither the students nor the professor are available."
✓ "Neither the students nor the professor is available."
(Verb agrees with closer subject)

There is/There are:
❌ "There is many reasons for this conclusion."
✓ "There are many reasons for this conclusion."

Run-On Sentences and Comma Splices

Run-On Sentences

Two independent clauses with no punctuation:
❌ "The study was well-designed the results were clear."

Fixes:
✓ "The study was well-designed. The results were clear."
✓ "The study was well-designed, and the results were clear."
✓ "The study was well-designed; the results were clear."

Comma Splices

Two independent clauses joined only by a comma:
❌ "The study was well-designed, the results were clear."

Fixes:
✓ Period: "The study was well-designed. The results were clear."
✓ Semicolon: "The study was well-designed; the results were clear."
✓ Conjunction: "The study was well-designed, and the results were clear."
✓ Subordination: "Because the study was well-designed, the results were clear."

Sentence Fragments

The Problem

Incomplete sentences lacking a subject, verb, or complete thought.

❌ "Because the sample size was too small."
✓ "Because the sample size was too small, the results were inconclusive."

❌ "For example, the results of the 2019 study."
✓ "For example, the results of the 2019 study supported this claim."

Intentional Fragments

Sometimes acceptable for emphasis in informal writing, but generally avoid in academic papers.

Pronoun Errors

Unclear Reference

❌ "Smith interviewed Jones about his theory."
Whose theory—Smith's or Jones's?
✓ "Smith interviewed Jones about Jones's theory."

Pronoun-Antecedent Agreement

❌ "Each student must submit their paper by Friday."
✓ "Each student must submit his or her paper by Friday."
✓ "Students must submit their papers by Friday."
(Plural often works better than awkward "his or her")

This/That Without Clear Reference

❌ "The data was incomplete and the methodology was flawed. This led to rejection."
This what?
✓ "The data was incomplete and the methodology was flawed. These problems led to rejection."

Comma Usage

Serial Comma (Oxford Comma)

❌ "The study examined age, gender and income." (ambiguous)
✓ "The study examined age, gender, and income." (clear)

Comma After Introductory Elements

❌ "After analyzing the data the researchers drew conclusions."
✓ "After analyzing the data, the researchers drew conclusions."

Commas with Restrictive/Non-Restrictive Clauses

Restrictive (essential information) – no commas:
"Students who studied regularly performed better."

Non-restrictive (extra information) – commas:
"The students, who had studied regularly, performed better."

Comma Overuse

❌ "The researcher, noted, that the data, was incomplete."
✓ "The researcher noted that the data was incomplete."

Apostrophe Errors

Possessives

❌ "The student's grades improved." (one student)
❌ "The students grades improved." (missing apostrophe)
✓ "The students' grades improved." (multiple students)

It's vs. Its

❌ "The study lost it's funding."
✓ "The study lost its funding." (possessive)
✓ "It's clear that more research is needed." (it is)

Plurals (Never Use Apostrophe)

❌ "The 1990's saw major changes."
✓ "The 1990s saw major changes."

Parallelism

The Rule

Items in a series should have the same grammatical form.

❌ "The study involved collecting data, to analyze results, and presenting findings."
✓ "The study involved collecting data, analyzing results, and presenting findings."

❌ "Researchers not only collected data but also the analysis was completed."
✓ "Researchers not only collected data but also completed the analysis."

Dangling Modifiers

The Problem

Modifier doesn't clearly connect to what it modifies.

❌ "Walking through the lab, the equipment was impressive."
(The equipment wasn't walking)
✓ "Walking through the lab, I found the equipment impressive."

❌ "After reviewing the literature, the hypothesis was developed."
✓ "After reviewing the literature, the researchers developed the hypothesis."

Misused Words

Affect vs. Effect

• Affect: usually a verb (to influence)


• Effect: usually a noun (a result)

✓ "The treatment affects outcomes." (verb)
✓ "The treatment has an effect on outcomes." (noun)

Which vs. That

• That: restrictive clauses (no comma)


• Which: non-restrictive clauses (comma)

✓ "The study that was conducted in 2020 showed..."
✓ "The study, which was conducted in 2020, showed..."

Fewer vs. Less

• Fewer: countable items


• Less: uncountable quantities

✓ "Fewer participants" / "Less time"

Between vs. Among

• Between: two items


• Among: three or more

✓ "Between the two groups" / "Among the participants"

Ensure vs. Insure vs. Assure

• Ensure: make certain


• Insure: provide insurance


• Assure: promise to a person

✓ "The method ensures accuracy."

Verb Tense Consistency

The Problem

Shifting tenses without reason.

❌ "The study examined three variables. Participants complete surveys."
✓ "The study examined three variables. Participants completed surveys."

Academic Conventions

• Present: General truths, current research ("Studies show...")


• Past: Completed research ("The study found...")


• Present perfect: Research with ongoing relevance ("Research has shown...")

Wordy Constructions

Reduce Wordiness

❌ "In the event that the data shows..."
✓ "If the data shows..."

❌ "Due to the fact that..."
✓ "Because..."

❌ "It is important to note that..."
✓ "Notably..." or just make the point

❌ "In order to..."
✓ "To..."

Proofreading Strategies

Read Aloud

Your ear catches errors your eye misses.

Read Backwards

Sentence by sentence—prevents auto-correcting in your head.

Focus on One Error Type

Make a pass for commas, then one for verb agreement, etc.

Use Tools (But Don't Trust Completely)

Grammarly, Word's grammar check—helpful but imperfect.

Take a Break First

Fresh eyes catch more errors.

Conclusion

Grammar errors undermine your credibility. Learn your weak spots, use proofreading strategies, and don't hesitate to seek help from writing centers or editing services. Clean prose lets your ideas shine.