Top 10 Grammar Blunders Professors Hate

Why this matters

Clarity isn't just style - it's part of the argument. Fix these errors and your writing becomes easier to read, more persuasive, and - yes - more likely to get a better grade.

1. Subject–Verb Agreement

Incorrect: The list of items are on the desk.

Why: The subject is list (singular), not items (plural).

Fix: The list of items is on the desk.

Tip: Identify the subject (not the noun inside a prepositional phrase) and match the verb to it.

2. Comma Splices

Incorrect: She studied all night, she still failed the test.

Why: Two independent clauses joined only by a comma.

Fixes: Split into two sentences, use a semicolon, or add a conjunction: She studied all night. She still failed the test.

Tip: If both halves can stand alone, don’t join them with only a comma.

3. Misplaced & Dangling Modifiers

Incorrect: Walking through the door, the cake was on the table.

Why: The modifier walking through the door appears to modify the cake.

Fix: Walking through the door, I saw the cake on the table.

Tip: Ensure modifiers attach clearly to the noun they describe - if it sounds odd, rewrite.

4. Apostrophe Errors (its / it's / plurals)

Incorrect: The dog wagged it's tail.

Why: it's = it is / it has; its = possessive.

Fix: The dog wagged its tail.

Tip: Try expanding it's to "it is" - if it fits, keep it's, otherwise use its.

5. Run-ons & Fused Sentences

Incorrect: I finished the paper I submitted it late.

Why: Two complete thoughts run together without punctuation.

Fix: I finished the paper, but I submitted it late.

Tip: If you can split into two sentences without losing meaning, do it.

6. Word Choice Confusion (affect / effect, their / there / they're)

Incorrect: The new policy will effect students negatively.

Why: effect is usually a noun; affect is usually a verb.

Fix: The new policy will affect students negatively.

Tip: When unsure, swap a simple synonym: if "influence" fits, use affect.

7. Sentence Fragments

Incorrect: Because the experiment failed.

Why: Dependent clause without a main clause.

Fix: Because the experiment failed, we repeated it using a new method.

Tip: Ensure every sentence has a subject + main verb that completes the thought.

8. Faulty Parallelism

Incorrect: She likes reading, to jog, and swimming.

Why: Mixed grammatical forms in a list (gerund / infinitive).

Fix: She likes reading, jogging, and swimming.

Tip: Make list items match grammatically - all -ing, all to-infinitives, etc.

9. Overuse / Misuse of Passive Voice

Problematic: The conclusion was reached by the researchers after many trials.

Why: Passive voice can hide the actor and weaken clarity (though sometimes appropriate).

Fix (clearer): The researchers reached the conclusion after many trials.

Tip: Use active voice when you want clarity and to show responsibility.

10. Tense Inconsistency

Incorrect: He studied the samples and then finds the result surprising.

Why: Mixing past and present confuses the timeline.

Fix: He studied the samples and then found the result surprising.

Tip: Pick a tense for the paragraph (usually past for methods/results) and stick to it.

Fixing these ten issues will immediately improve clarity and presentation in most student papers. Use the one-line tips for a quick triage and then perform a final human proofread.

FAQ

Can I rely on grammar checkers to catch everything?

Grammar checkers catch many surface errors, but they miss context-based mistakes (wrong word choice, logic errors). Always do a final human read and check meaning, not just form.

What's the fastest fix for comma splices?

Split into two sentences, add a semicolon, or insert a coordinating conjunction (and, but, so). Choose the one that best preserves rhythm and meaning.

Is passive voice always wrong?

No - passive voice is useful when the actor is unknown or unimportant (e.g., methods sections). Prefer active voice for clarity and stronger writing where the actor matters.

How can I stop mixing tenses?

Decide whether you’re describing past work (research methods/results) or general truths. Stick with past for completed actions, present for general facts. Re-read each paragraph for consistency.

Any quick memory trick for its vs. it's?

Try expanding it's to it is or it has. If that works, it's is correct; otherwise use its.