Some English mistakes show up in academic writing far more often than others — not because writers don’t know the rule, but because the rule is genuinely inconsistent or doesn’t have an equivalent in many other languages. Here are twelve of the most common ones we see in academic manuscripts and theses, with quick fixes for each. For the bigger picture on academic register, verb tense, and hedging language, see our full academic English writing guide.
1. “Research” as a Countable Noun
Incorrect: “a research,” “many researches.” Fix: “research” is uncountable in English — use “research” (singular, no article) or “studies” when you mean multiple individual pieces of work: “several studies have examined this,” not “several researches have examined this.” Also uncountable in the same way: “evidence,” “knowledge,” and “information.”
2. Confusing “Affect” and “Effect”
Fix: “Affect” is usually a verb (“smoking affects lung function”); “effect” is usually a noun (“the effect of smoking on lung function”). A quick trick: if you need a verb, it’s almost always “affect.” (There’s a rarer sense where “effect” is a verb meaning “to bring about” — “to effect change” — but this is uncommon enough to avoid if you’re unsure.)
3. Comma Splices
Incorrect: “The results were significant, this supports the hypothesis.” Fix: join two complete sentences with a period, a semicolon, or a conjunction — not just a comma: “The results were significant; this supports the hypothesis,” or “The results were significant, and this supports the hypothesis.”
4. Dangling Modifiers
Incorrect: “After analyzing the data, the results were surprising.” (This implies the results analyzed the data.) Fix: make sure the subject of the main clause is the one performing the action in the introductory phrase: “After analyzing the data, we found the results surprising.”
5. Its vs. It’s
Fix: “It’s” always means “it is” or “it has.” “Its” (no apostrophe) is possessive: “The study reported its findings” (not “it’s findings”). Since contractions are generally avoided in formal academic writing anyway, “it’s” should rarely appear at all.
6. Overusing the Passive Voice
Some passive voice is normal and even preferred in methods sections (“Participants were recruited from…”), but overusing it throughout a paper makes writing harder to follow. Fix: use active voice where the actor matters to the point you’re making: “We analyzed the data using SPSS” is often clearer than “The data were analyzed using SPSS,” though check your target journal’s preference.
7. “Data” as Singular
Formally, “data” is the plural of “datum,” so careful academic style often treats it as plural: “the data show” (not “the data shows”). This is genuinely shifting in modern English and many journals now accept “data” as singular — but in strict academic style, plural is safer.
8. Confusing “Fewer” and “Less”
Fix: “fewer” for countable things (“fewer participants”), “less” for uncountable quantities (“less time,” “less variance”).
9. Misplacing “Only”
“Only” changes meaning depending on where it sits: “Only the treatment group improved” (no other group did) vs. “The treatment group only improved” (it didn’t do anything else, like decline). Fix: place “only” directly before the word or phrase it’s meant to modify.
10. Mixing British and American Spelling
Incorrect: using “analyze” and “colour” in the same document. Fix: pick one variant (usually whichever your target journal or university uses) and apply it consistently — including in less obvious word pairs like “organization/organisation” and “center/centre.” Your word processor’s spell-check language setting can catch most of these automatically if set correctly for the whole document.
11. Wordy, Redundant Phrases
Academic writing sometimes drifts toward padding that adds length without adding meaning. Fix: “due to the fact that” → “because”; “in order to” → “to”; “a large number of” → “many”; “at this point in time” → “now” or “currently.” Trimming these makes writing more direct without losing precision — reviewers generally read concise writing as more confident, not less thorough.
12. Subject-Verb Agreement With Collective Nouns and Intervening Phrases
Incorrect: “The list of participants were reviewed.” Fix: the verb agrees with the actual subject (“list”), not the noun closest to it (“participants”): “The list of participants was reviewed.” This mistake is especially common when a long prepositional phrase sits between the subject and the verb.
Frequently Asked Questions
Are these rules the same in British and American academic English? Most of the grammar rules above apply in both varieties — the differences are mainly in spelling and a handful of vocabulary choices, not sentence structure or these specific grammar points.
Will a grammar checker catch all of these? Automated tools catch some (comma splices, some subject-verb agreement issues) reliably, but miss others — misplaced “only,” dangling modifiers, and register issues like wordiness often require a human read-through.
Catching these consistently across a full thesis or manuscript — especially the subtler ones, like dangling modifiers and misplaced “only” — is exactly the kind of detail work a fresh pair of eyes catches faster than the person who’s been staring at the document for months. If you’d like a professional read-through before you submit, get in touch — our formatting and editing services cover language issues alongside formatting.