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Roxanne K. Young

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Merriam-Webster’s Collegiate Dictionary defines an abbreviation as “a shortened form of a written word or phrase used in place of the whole”3 (eg, Dr for doctor, US for United States, dB for decibel).

An acronym is “formed from the initial letter or letters of each of the successive parts or major parts of a compound term”3 (eg, ANCOVA for analysis of covariance). Acronyms are pronounced as words.

An initialism is “an abbreviation formed from initial letters” and pronounced either as a separate word3 (eg, PAHO for Pan American Health Organization) or as a set of consecutive initials (eg, NSF for National Science Foundation).

Overuse of abbreviations can be confusing and ambiguous for readers—especially those whose first language is not English or those outside a specific specialty or discipline. However, since abbreviations save space, they may be acceptable to use when the original word or words are repeated numerous times.

Instructions for authors published in medical and scientific journals may include guidelines on the use of abbreviations, ranging from “limit of 4 per manuscript” to “use only approved abbreviations.” Authors, editors, manuscript editors, and others involved in preparing manuscripts should use good judgment, flexibility, and common sense when considering the use of abbreviations. Abbreviations that some consider universally known may be obscure to others. Author-invented abbreviations should be avoided. See specific entries in this section and 15.0, Nomenclature, for further guidance in correct use of abbreviations.

Note: The expanded form of an abbreviation is given in lowercase letters, unless the expansion contains a proper noun, is a formal name, or begins a sentence (capitalize first word only).

Style for abbreviations used in JAMA and the Archives Journals rarely calls for the use of periods. (But: See 14.6, Names and Titles of Persons.)

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