Writing 6 min read

Common Grammar Mistakes in Scientific Writing

Scientific writing has its own grammar rules — some standard, some specific to academic and research contexts. Many researchers, especially those writing in English as a second language, make the same mistakes repeatedly. Reviewers notice. Editors notice. And these errors can distract from otherwise excellent science.

This guide covers the most common grammar problems found in research papers and shows you exactly how to fix them.

1. Tense inconsistency

Different sections of a research paper use different tenses — and mixing them up is one of the most common errors.

  • Introduction — present tense for established facts, past tense for previous studies
  • Methods — past tense (you describe what you did)
  • Results — past tense (you describe what you found)
  • Discussion — present tense for your interpretation, past for specific results
  • Conclusion — present tense

❌ Wrong

"Samples are collected and stored at −20°C. We analyse them using HPLC."

✅ Correct

"Samples were collected and stored at −20°C. They were analysed using HPLC."

2. Article errors (a, an, the)

Articles are one of the hardest parts of English for non-native speakers. The rules are complex, but a few patterns cover most cases in scientific writing.

Use the when referring to something specific or already mentioned. Use a/an when introducing something for the first time or referring to one of many.

❌ Wrong

"A HPLC method was developed. Method showed good linearity."

✅ Correct

"An HPLC method was developed. The method showed good linearity."

Note: use "an" before words starting with a vowel sound — "an HPLC method" (H is pronounced "aitch"), "an hour", "a university" (sounds like "you").

3. Passive voice overuse

Passive voice is appropriate in scientific writing — particularly in Methods. But overusing it across all sections makes writing feel flat and impersonal. The Discussion and Conclusion sections especially benefit from more active, direct sentences.

❌ Overused passive

"It was found that the compound was degraded when it was exposed to light. It is suggested that storage in dark conditions should be recommended."

✅ More direct

"The compound degraded upon light exposure. We recommend storage in dark conditions."

4. Wordiness and redundancy

Scientific writing should be precise and concise. Many common phrases add length without adding meaning.

  • "due to the fact that" → because
  • "in order to" → to
  • "it is important to note that" → notably or just delete it
  • "a total of 30 samples" → 30 samples
  • "conducted an investigation into" → investigated
  • "at this point in time" → now

5. Sentence structure problems

Run-on sentences

❌ Wrong

"The samples were prepared and then they were injected into the HPLC system and the chromatograms were recorded and peak areas were calculated."

✅ Correct

"The samples were prepared and injected into the HPLC system. Chromatograms were recorded and peak areas calculated."

Dangling modifiers

❌ Wrong

"Having been dissolved in methanol, the analyst injected the sample." (The analyst was not dissolved in methanol.)

✅ Correct

"After the sample was dissolved in methanol, it was injected."

6. Subject-verb agreement

When a collective noun or a complex subject is used, the verb form is often wrong.

❌ Wrong

"The number of samples were 30." / "Data was collected over three days."

✅ Correct

"The number of samples was 30." / "Data were collected over three days." (data is plural)

A quick self-editing checklist

Check your scientific writing on Scitero

The Scitero Grammar Checker catches passive voice, tense errors, wordiness and scientific tone issues — free, no sign up.

Open Grammar Checker →