Grammar mistakes in academic writing do more than cost marks — they undermine the credibility of your argument. A reader who notices repeated errors begins to question the care taken with the research itself. The good news is that the same mistakes appear again and again in student writing. Learn to fix these ten, and you will eliminate the majority of grammar errors in your work.
1. Subject-Verb Agreement Errors
The verb must agree with its subject in number. Singular subjects take singular verbs; plural subjects take plural verbs. This breaks down most often when the subject and verb are separated by a long phrase.
Wrong: "The impact of social media on young people's mental health have been widely studied."
Right: "The impact of social media on young people's mental health has been widely studied."
The subject is "impact" (singular), not "people" — the phrase in between is a modifier. Strip out the modifying phrase to check agreement: "The impact… has been studied."
2. Incorrect Use of Apostrophes
Apostrophes indicate possession or mark contractions. They are never used to form plurals.
- Possession: the researcher's findings (one researcher), the researchers' findings (multiple researchers)
- Contraction: it's = it is; its = belonging to it
- Never: result's, finding's, data's as plurals — these are wrong
The its/it's distinction is one of the most common errors in all writing. Remember: if you can replace it with "it is," use it's. Otherwise use its.
3. Comma Splices
A comma splice joins two independent clauses with only a comma — which is not strong enough punctuation to connect two complete sentences.
Wrong: "The results were inconclusive, further research is needed."
Right (three options):
- "The results were inconclusive; further research is needed." (semicolon)
- "The results were inconclusive, and further research is needed." (coordinating conjunction)
- "The results were inconclusive. Further research is needed." (two sentences)
4. Dangling Modifiers
A dangling modifier is a descriptive phrase that does not logically attach to the noun it is supposed to modify.
Wrong: "Having reviewed the literature, the gap in research became clear."
The gap did not review the literature — the researcher did.
Right: "Having reviewed the literature, the researcher identified a clear gap."
When a sentence begins with a participial phrase ("Having reviewed…", "After analysing…"), the subject immediately following must be the person or thing performing the action.
5. Incorrect Tense Consistency
Academic writing uses specific tenses for specific purposes. Switching between them inconsistently is a common error.
- Literature review: past tense for what researchers found — "Smith (2023) found that…"
- Your own current study: present tense — "This paper argues that…"
- Methods: past tense — "Participants were recruited through…"
- Results: past tense — "The analysis revealed…"
- Established facts: present tense — "Water freezes at 0°C."
6. Vague Pronoun Reference
A pronoun must have a clear, unambiguous antecedent. When "it," "this," "they," or "which" could refer to more than one thing, the sentence is unclear.
Vague: "The government introduced the policy after the report was published. This caused significant debate."
What caused debate — the policy, the report, or the act of publishing it?
Clear: "The government introduced the policy after the report was published. The policy caused significant debate."
7. Run-On Sentences
A run-on sentence joins two or more independent clauses without appropriate punctuation or connectors. Unlike comma splices, run-ons often have no punctuation at all between clauses.
Wrong: "The study involved 200 participants they were recruited from three universities the data was collected over six months."
Right: "The study involved 200 participants recruited from three universities. Data was collected over a six-month period."
8. Misuse of "Which" vs "That"
In formal academic writing, "that" introduces essential clauses (no comma needed) and "which" introduces non-essential clauses (preceded by a comma).
"That" — essential: "The study that used the largest sample produced the most reliable results."
Removing "that used the largest sample" changes the meaning — it is essential information.
"Which" — non-essential: "The 2023 study, which used a sample of 500, produced reliable results."
Removing "which used a sample of 500" does not change the core claim — it is additional information.
9. Double Negatives
Standard academic English does not use double negatives. Two negatives logically cancel each other out, producing an unintended positive meaning.
Wrong: "The researchers did not find no significant difference."
This literally means they did find a significant difference.
Right: "The researchers found no significant difference." or "The researchers did not find a significant difference."
10. Incorrect Use of Semicolons
Semicolons connect two independent clauses that are closely related. They cannot connect a clause to a phrase, and they should not be used where a comma is sufficient.
Correct: "The sample size was small; the results should be interpreted with caution."
Both sides of the semicolon are complete sentences.
Wrong: "The study had several limitations; including a small sample size."
"Including a small sample size" is not an independent clause — use a comma instead.
A Quick Self-Editing Routine
- Read your paper aloud — your ear catches errors your eye misses
- Check every sentence with "it," "this," "they," or "which" — is the reference clear?
- Find every comma — is it joining two complete sentences without a conjunction? Fix the comma splice.
- Check apostrophes in every possessive and contraction
- Run a grammar checker as a final pass to catch anything you missed
Good grammar does not make a good argument — but bad grammar can undermine one. Your ideas deserve to be heard clearly.
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