Abbreviations, Acronyms, and Initialisms
An abbreviation is a truncated word; an acronym is made up of parts of the phrase it stands for and is pronounced as a word (ELISA, AIDS, GABA); an initialism is an acronym that is pronounced as individual letters (DNA, RT-PCR). For the purposes of this section, “abbreviation” will refer to all of these.
Do not introduce an abbreviation in a heading. Abbreviations can, however, be used in a heading if previously established.
Abbreviations should be written out in Affiliations and Acknowledgments (unless abbreviated in text). Affiliations may be abbreviated at the author’s discretion in the Address for Correspondence.
When writing out affiliations, use the official spelling, which may or may not be American spelling. Words to look for are Programme vs. Program, Centre vs. Center, Organisation vs. Organization.
- WHO, World Health Organization
- OIE, World Organisation for Animal Health
Avoid excessive abbreviations. Use standard abbreviations only; do not make up abbreviations. Spell out on first mention and use only if it occurs a substantial number (>3 times) of times (subject to editorial discretion). Some specific examples follow:
Spell out amino acid when followed by words; abbreviate aa without definition when paired with numbers (absolute or percentage).
Define Ct at first use. Use subscript "t"
Spell nucleotide when followed by words; abbreviate nt without definition when followed by numbers (absolute or percentage).
reverse transcription PCR
Spell reverse transcription at first use; do not use an en dash between reverse transcription and PCR. If the term is used >3 times, the abbreviation RT-PCR can be used.
real-time reverse transcription PCR
Spell real-time reverse transcription at first use; use a hyphen in the term real-time, but do not use an en dash between reverse transcription and PCR. If the term is used >3 times, the abbreviation rRT-PCR can be used.
Avoid SOB (shortness of breath, sulfur-oxidizing bacteria), if possible.
Use STI for sexually transmitted infection but not for soft tissue infection (SSTI okay for skin and soft tissue infection).
No. (vs. number)
In text, use “number” when followed by a word, “no.” when followed by a numeral.
We assigned GenBank accession numbers.
We submitted it under GenBank accession no. ABC123.
See the section on Acronym Use with Virus Names
Abbreviations/Initialisms That Should Not To Be Spelled Out in Text and
Titles In the Text
The following are used without spelling out on first mention (list not comprehensive).
aa (when followed by numbers [absolute or percentage])
AMP, ADP, ATP
BCG (but at first mention specify Mycobacterium bovis BCG)
bp, kb, kbp (when used with a numeral, but spell out when not used with a numeral)
BSE (can be used in the title if "bovine spongiform encephalopathy" is used in the abstract or, for letters, in the first paragraph of the text; can be used in the running head)
CSIRO (The Commonwealth Scientific and Industrial Research Organisation, the national government body for scientific research in Australia)
DDBJ (DNA Data Bank of Japan)
DNA, RNA, cDNA, mRNA, tRNA, or rDNA (Note: c, complementary; m, messenger; t, transfer; r, ribosomal)
dNTPs (deoxynucleotide triphosphates)
EMBL (European Molecular Biology Nucleotide Sequence Database)
F, M (male, female; use abbreviations in tables and figures only; write out in text)
Ig and IgA, IgD, IgE, IgG, and IgM
kbp, kb, and bp (when used with a numeral, but spell out when not used with a numeral)
M, F (male, female; use abbreviations in tables and figures only; write out in text)
PCR (Also see reverse transcription PCR and real-time reverse transcription PCR in the section above.)
ppb, ppm, ppt
RNA, DNA, cDNA, mRNA, tRNA, or rDNA (Note: c, complementary; m, messenger; t, transfer; r, ribosomal)
SD, SE, SEM
SI units used with a numeral are never spelled out.
sp., spp., sp. nov (with organism name), subsp. (preferred over ssp.)
UK (when used as an adjective; write out when used as a noun)
US (when used as an adjective; write out when used as a noun)
vol/vol, wt/vol, wt/wt
vs. (can be abbreviated when used inside parentheses; otherwise, spell out)
In the Title
In long titles, the following abbreviations can be used without being spelled out, provided the terms are spelled out in the Abstract or, for letters, in the first paragraph. These terms may also be used in running heads.
In instances when an abbreviation has become the de facto name, spelling out may cause confusion, particularly if the term appears only once. In these instances, write the abbreviation, then spell out in parentheses, even if it appears only once in the article. On subsequent occurrences, use the abbreviation
VDRL (Venereal Disease Research Laboratory) test
The article “a” or “an” should match the sound of the abbreviation or acronym, not the word for which it stands.
an HMO report, a MRSA infection (usually pronounced Mersa), a NICU (usually pronounced nick-you)
However, articles are often omitted in front of abbreviations.
CDC, not the CDC
Abbreviate the following in tables, figures, and in the Methods section of research articles. Exception: Write out in research articles if not preceded by number or if used alone; i.e., not part of a “recipe.”
Abbreviate Street when part of address, with no period.
265 Peachtree St, Atlanta, GA
Abbreviate Saint, with period.
St. Louis encephalitis
Abbreviate UK and USA when used as part of an address, e.g., affiliations and address for correspondence.
Define ICD code revisions as follows:
International Classification of Diseases, 10th revision (ICD-10)