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Editing Tip: Proper Usage of Latin Terms

  • Latin terms such as e.g. or in vitro are extensively used in scientific writing
  • Keep in mind that e.g. and i.e. are not combined with etc.

Latin terms are extensively used in scientific writing. Although these words and phrases may help to convey meaning concisely, they may also obscure meaning due to misuse. Additionally, despite seeming sophisticated, certain Latin terms may in fact be too informal for manuscripts and other technical writing. Below, we review the meaning and proper usage of a few Latin words and phrases that are commonly misused and/or overused in the sciences. In all cases, note that italicization is increasingly considered optional by journals.

###et al.

This phrase, an abbreviation for et alia, literally means “and others.” It should be used to indicate that the names of authors have been omitted from a citation, and not to denote other excluded content or to serve as a substitute for etc. (see below) in a list. Note that a period is never placed after et, whereas al., as an abbreviation for alia, is typically followed by a period.

Moreover, a comma is included before et al. only if the term follows a list of two or more names (as in “Jones, Baker, et al. found that...,” but not in “Jones et al. found that...”).


This abbreviation represents the phrase et cetera, which essentially means “and so forth” and is usually used at the end of a truncated list. The correct punctuation is a comma before etc. in any context and after etc. if not at the end of a sentence (as in “a stacking gel, a loading gel, etc., were prepared”). Overuse of this term should be avoided in formal scientific writing, however, because etc. is considered vague. Where possible, it should thus be either omitted altogether or replaced with a more specific term (as in “a stacking gel, a loading gel, and other items were prepared”).


The abbreviation e.g. stands for exempli gratia, meaning “for example,” and precedes one or more examples, rather than a comprehensive list. Note that etc. is never needed after the abbreviation e.g., which already indicates that only a few examples, and not all instances, will be cited.

This term is most frequently followed by a comma, and the entire construction (e.g. + example(s)) should be enclosed by two commas or parentheses (as in “several proteins, e.g., IL-1 and TNF-a, were analyzed by ELISA” or “several proteins (e.g., IL-1 and TNF-a) were analyzed by ELISA”) because this text is a nonrestrictive element.


The abbreviation i.e. represents the Latin phrase id est, or “that is.” It should not be used interchangeably with e.g.; rather, i.e. is used for restatement or clarification (as in “we studied two proteins, i.e., IL-1 and TNF-a”). As the information following i.e. is comprehensive, again, etc. should not be used in this context. This abbreviation adheres to the same conventions of comma usage as for e.g.


The word versus, also written as vs. or v. (primarily for US Supreme Court cases), means “against” and is used for contrast. This term is best applied when briefly comparing data parenthetically (“(5 µg versus 4 µg, respectively)”) or describing the axes of a graph (“this is a plot of arbitrary intensity units versus concentration”).

Otherwise, other terms are considered more appropriate for formal scientific writing, such as “in contrast to” or “compared with.” For example, “we assessed the treatment group versus the control group” could be revised to “we assessed the treatment group compared with the control group” for clarity and formality.

###in vitro, in vivo, ex vivo, in situ, in silico

These Latin terms literally mean “in glass” (outside a living organism and within the laboratory, such as cells in culture), “in a living thing,” “outside a living thing,” “in place” (or “in its original position”), and “in silicon” (on a computer or by computer simulation), respectively.

  • Note that in vitro and ex vivo do not have the same meaning; in vitro research relies on samples decoupled from their source and potentially altered, such as an immortalized cell line, whereas ex vivo research relies on unaltered tissue or cells taken directly from an organism.
  • Meanwhile, in a biological context, in situ may be most akin to ex vivo, particularly if an intact tissue is studied under near-native conditions in the laboratory, or to in vivo if it implies localization within the body (such as “ductal carcinoma in situ,” meaning noninvasive breast cancer localized to the ducts).

We hope that today’s editing tip has clarified how and when to use several frequently employed Latin terms in scientific writing. If you have any comments or questions, please contact us. AJE wishes you the best in your writing endeavors!

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