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When to Stop Defining Abbreviations

Back when I taught copyediting, my students once asked me when it would be OK to not spell out an abbreviation that doesn’t appear in the dictionary. I appreciated their confusion, because it is sometimes difficult to define an exception to the rule.

We used The Chicago Manual of Style in the course I was teaching, and even CMoS isn’t entirely clear on what the exceptions would be (17th ed., 10.3)

A number of expressions are almost always abbreviated, even in regular prose, and may be used without first spelling them out. Many of these will be listed as main entries with pronunciation (labeled as nouns rather than as abbreviations) in the latest edition of Webster’s.

What are those other exceptions? Does it depend on the audience?

For example, our midterm was an article written for marketing and sales professionals and included the abbreviations B2B, B2C, and CMO. Students had to create a style sheet and follow Chicago and Merriam-Webster’s Collegiate Dictionary. They needed to determine what to do with those abbreviations.

Certainly, a publication may choose to never spell out certain abbreviations its audience is very familiar with, keeping in mind those readers new to the publication or industry. The exceptions should be listed in the publication’s style sheet.

But what if you don’t get a style sheet with the project? Can a copyeditor decide when an abbreviation has reached some critical mass of understanding with a manuscript’s readership?


Start by checking similar publications to see what other editors have decided. When the RSS technology was first introduced, the publication I worked for spelled out the abbreviation on first use (rich site summary, at that time). We did the same for blog, spelling it out as Web blog on first use. Once the abbreviations became more popular than their spelled-out forms in publications and forums, we dropped the spelled-out forms, too. It was a decision we made as an editorial team.

Keep in mind that readers new to the topic might need a few more signposts than readers with more experience. What’s the ratio of beginners to experienced in your audience?

If you think readers will know the abbreviation and feel insulted that it’s been spelled out, don’t just make the change. Instead, query. Present your argument to the author or supervising editor. Encourage that any exceptions to the spell-it-out rule be done consistently and incorporate them into the publication’s style going forward.

When in doubt, though, spell it out.

A version of this article originally published on May 28, 2013, on


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