Subtle Grammatical Usage Notes

aka Common mistakes when writing scientific papers and grants.

Usage

• 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.
• 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)
• 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".
• Where / Wherein
  Use wherein when you can replace with "in which" or "in what".

Punctuation

• Hyphen, en dash, em dash