I noticed that proper nouns, such as names of theorems or techniques are often set in italics in scientific writing but not always. Are there rules about it, for example each proper noun should be set in italic the first time it occurs?

A contrived example

There are many different methods for adding two numbers:

Very Simple Addition (VSA) works by calculating a+b.

Unnecessary Complicated Addition (UCA) works by calculating -(-a-b).

VSA is the method used by everyone but the British who use UCA because of tradition along with their foot-inch based measurement system.

  • Can you give an example?
    – jschabs
    Commented Apr 17, 2014 at 18:57
  • Do you mean in a journal? In textbooks, this is often done to indicate keywords or glossary entries.
    – dmm
    Commented Apr 18, 2014 at 4:38
  • Generally, the right approach is to ask which Formatting and Style Guide your scientific body uses, and then follow that guide. It provides the answer in minuscule details, much finer than you'd ever find here (and probably much finer than you'd have to your liking...)
    – SF.
    Commented May 19, 2014 at 9:31

3 Answers 3


The Style Manual of the American Psychological Association (APA, 2009, pp. 104-106) is very clear on the use of italics. Note especially the bold section (bold emphasis mine):

Use italics for

  • titles of books, periodicals, films
    exception: italic words in the title (reverse italicization)
  • genera, species, and varietes
  • introduction of a new technical term
    (after a term has been used once, do not italicize it)
  • a letter, word, or phrase cited as a linguistic example
    ("words such as big and little")
  • words that could be misread
    ("the small group", meaning a designation, not group size)
  • letters used as statistical symbols or algebraic variables
  • some test scores and scales
  • periodical volume numbers in reference lists
  • anchors of scale
    ("health ratings ranged from 1 (poor) to 5 (excellent)")

Do not use italics for

  • foreign phrases and abbreviations common in English
  • chemical terms
  • trigonometric terms
  • nonstatistial subscripts to statistical symbols or mathematical expressions
  • Greek letters
  • mere emphasis. (Italics are acceptable if emphasis might otherwise be lost; in general, however, use syntax to provide emphasis.)
    it is important to bear in mind that this process is not proposed as a stage theory of developments.
  • letters used as abbreviations

I've been writing both in APA and MLA style, and I have never needed to emphasize words. Scientific discourse is encouraged to be neutral and self-constrained, and there are other, semantic, means to direct the reader's attention.

  • 1
    Correction: Scientific names for organisms (in the form: Genus species, or G. species) are italicized, regardless of their linguistic roots. Common names for organisms are not italicized.
    – dmm
    Commented May 20, 2014 at 17:31
  • what is the correct usage of the emboldened bullet?
    – Ooker
    Commented Feb 1, 2015 at 10:05

Italics are a common way to emphasize words. As such, it's best to use italics sparingly. A text where every proper noun is italicized gets very annoying to read; it'd be like listening to a commercial.
If you're writing for a specific publication, check their style guide.


Italics are used to emphasize words in general writing, but in technical writing you may have to use them for other forms of distinctive treatment. For that reason, I do not use italics (or bold) for emphasis. Generally, I use bold to highlight terms that I think the reader won't know. I only use italics when my style guide calls for them. I generally ignore Chicago, MLA, and so forth for rules regarding distinctive treatment, unless my own style guide doesn't say anything. Even then, I discuss the style rules I use with the other people on my team before I put them into force.

Remember that concise, clear, and consistent documentation is our goal. Correct style is subservient to that goal. Other technical writers may question your choice, but readers won't be conscious of it.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.