Subtle Grammatical Usage Notes

aka Common mistakes when writing scientific papers and grants.


  • Alternate / Alternative
    Alternate means "every other one" in a series. Alternative means "another option". (REL)
  • Bacteriophage / Bacteriophages
    Even though it sounds strange, the plural of bacteriophage is really bacteriophages.
  • Because / Since
    Since implies that time has passed. If you are using it correctly, you should be able to substitute "after" in its place and preserve the meaning of a sentence. Otherwise, you should be using because to join your two clauses.
  • By Contrast / In Contrast
    Use By contrast when the next word is a noun. Use In contrast when followed by a preposition such as "with" or "to". (REL)
  • Complimentary / Complementary
    Complimentary means praising or free of charge. Two things are complementary when they combine in a way that enhances each other's qualities or if they are nucleic acid bases that pair with each other. Thus, "complementary base", "complementary skills", "complimentary comments".
  • This Data / These Data
    Use this data when you can replace "data" with "information". Use these data when you can replace "data" with "facts". (source)
  • gram-negative/gram-positive bacteria
    The Gram in Gram staining is a proper noun. It's generally agreed that Gram stain is capitalized, but many sources say that Gram should not be capitalized when describing gram-positive/gram-negative bacteria.
  • Growth media/medium
    The first is plural and the second is singular. Try substituting "solution" or "solutions" into the sentence to see which one sounds right. Use medium when referring to one formulation (e.g., "Cultures were grown in LB medium.") Use media when referring to multiple different formulations. (e.g., "Cultures were grown on media supplemented with either 10 or 25 mg/ml tryptophan.") Also use medium when referring to a certain amount (e.g., "25 ml of M9 minimal *medium*").
  • Principle / Principal
    Principle means the fundamental basis of a fact. A Principal is the main player or the person of most importance in a project. Thus, "proof of principle", "principal investigator", "in principle", "the principle reason", "school principal".
  • Regardless / Irregardless
    Regardless is correct. Irregardless is a commonly heard but incorrect term, probably originating due to similar word pairs like respective / irrespective.
  • Where / Wherein
    Use wherein when you can replace with "in which" or "in what".


  • Generally the best way to use Greek letters, etc., is to use the "Insert symbol" command in a program (like Word or Illustrator), rather than symbol font. This generally causes fewer problems across programs or platforms.
  • Hyphen, en dash, em dash
    • Do not use a hyphen (-78) in mathematical expressions where a minus sign (78) should be used.
  • Prime symbol versus single quote or apostrophe: 5′ not 5' end of a DNA sequence.


  • Claims of Novelty and Priority. One should avoid claims that your study was the first to do something new. Even if true, these statements are generally subjective and hard to prove. They also tend to draw the ire of reviewers. You might say things like "our method enables X which Y and Z cannot do" instead of "our novel method allows X for the first time". From the PNAS Information for Authors: "Statements of novelty and priority are not permitted in the text." Related words and phrases: "unprecedented", ....
  • "Well-known", "famous", "celebrated"... While it may be this to you since you are an expert in the field, it might not be to the reviewer or average reader of your paper. Would it really be "well-known" in 50 years when someone is reading your paper?

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Topic revision: r13 - 24 Dec 2014 - 19:50:24 - Main.JeffreyBarrick
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