Hyphens and Dashes in AMA Style

Jun 06, 2021
9 min read

The AMA Manual of Style (11th edition) is an academic style guide widely used in the medical sciences. As an academic proofreader, then, you may need to learn the basics of this style. And, having previously introduced the AMA referencing system, this post will focus on how to use hyphens and dashes in AMA style.

Hyphenated Compounds in AMA Style

AMA style follows all of the standard rules for hyphenating compound words, which you should be broadly familiar with as a proofreader. This includes hyphenating when using a compound adjective before a noun (e.g., high-density lipoprotein).

However, there are also a few additional rules about compound words in AMA style that you should be aware of when proofreading:

If a compound adjective contains a number as its second element, it should not be hyphenated (e.g., type 2 diabetes, not type-2 diabetes).
Some compounds should never be hyphenated, such as those including disease names or chemical compounds used as adjectives (e.g., hydrogen sulfide solution, not hydrogen-sulfide solution).
The word “email” is not hyphenated in AMA style, but all other words using the “e-” prefix to mean “electronic” are (e.g., e-cigarette, e-banking).
Some technical terms and phrases in medical writing are conventionally hyphenated. The AMA recommends checking the Merriam-Webster Collegiate Dictionary, Dorland’s Medical Dictionary or Stedman’s Medical Dictionary if you are unsure about such terms.

In addition, when a numerical range is used as a modifier before the word it modifies, both figures in the range should be hyphenated (e.g., a 6- to 8-week course).

Keep an eye out for compounds of these types in writing that uses AMA style.

Using Hyphens to Indicate Ranges

Unlike many academic style guides, AMA style does not suggest using en dashes in numerical ranges (for more on en dashes, see below). Rather, it suggests using the word “to” for any numerical range mentioned in the main text of a document:

Around 15% to 20% of users report side effects. ✓

However, AMA style also recommends using a hyphen for ranges that:

Include academic or financial years, life spans, or study spans (e.g., The 2012-2013 academic year was notably productive).
Are given in parentheses, a figure, or a table.

The key exception here is when a range within parentheses, a figure, or a table includes a negative number. In such cases, the range should be indicated with “to” due to the similarity between a hyphen and the minus symbol:

The results span a large temperature range (−10-5 degrees). ✗

The results span a large temperature range (−10 to 5 degrees). ✓

If your client has used a hyphen alongside a minus sign like this, you should suggest replacing the hyphen with “to” regardless of where it appears in the document.

Using En Dashes in AMA Style

Other style guides may suggest using en dashes to denote numerical ranges. But in AMA style they serve only one purpose: to clarify complex compound modifiers.

This applies when a compound modifier includes an open or hyphenated compound, or when the term modified is a compound (e.g., t-cell–specific, post–World War I).

As a proofreader, then, you should not only make sure an en dash is present in such compounds, but also that your client has not used an en dash in any other context.

Using Em Dashes in AMA Style

AMA style permits the use of the longer em dash to set apart parenthetical information, or to indicate a significant interruption in a thought:

Schrödinger’s cat—be it living or dead—is a staple of popular science.

Em dashes can also be used to separate the referent from the subject of a clause:

Curie, Goodall, Franklin—these scientists have inspired women in STEM.

However, em dashes should also be used sparingly. As a proofreader, then, you might want to suggest using another form of punctuation, such as parentheses, commas, or a colon (as appropriate), if a document has many em dashes.

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