Overview

Abbreviations, which include contractions and acronyms, usually make an author’s job easier. However, they reduce readability for those unfamiliar with the terms. Accordingly, the general advice is to keep abbreviations to a minimum. However, there are exceptions.

when to use

There are no strict rules governing abbreviation use, although convention dictates that a term should be used at least 3–5 times in a paper for an abbreviation to be considered worthwhile. Thus, if a term is used just a couple of times in a paper, it should be used in full and not abbreviated unless the full term is long and unwieldy. All terms to be abbreviated should be defined upon first use, except when they first occur in a title or heading. Any abbreviations used in abstracts will have to be re-defined within the text itself.

When not to use

Abbreviations should be avoided in article titles, unless the abbreviation itself is well known. Furthermore, if the first use of a term to be abbreviated occurs in a title, heading, or subheading, it should be defined at its next use in the text itself. Abbreviations should be kept to a minimum in abstracts. Some journals, such as the American Journal of Respiratory and Critical Care Medicine, request that abbreviations be completely avoided in the abstract.

no definition Needed

Several common abbreviations can be used without explanation, such as DNA, RNA, and AIDS. Some journals, particularly specialist journals, provide a list of abbreviations that are acceptable to use without definition. For example, Endocrine Reviews provides a list of abbreviations that are common in the field, some of which (e.g., BSA, DNA, EDTA, mRNA) would also be acceptable without explanation in other journals. However, some, such as FSH, MSH, and RIA, would not typically be understood by readers of other journals. Similarly, the Journal of Biological Chemistry provides a list of abbreviations that are permitted without explanation in the article text (e.g., ALS, DTT, HPLC); abbreviations can be used without explanation in titles but "authors should strive to limit abbreviations for clarity". Meanwhile, Liver Transplantation states that abbreviations “not requiring definition are those listed in the American Medical Association Manual of Style”.

Table and Figures

The issue of abbreviations in tables and figures is complex and there is no clear guideline on their use. Generally, once an abbreviation is defined, it does not need to be re-explained, which means that all abbreviations used in tables and figures do not need to be explained in the table footnotes or figure legends if the abbreviation has been expanded upon in the text. Although few journals explicitly state this, some do: for example, Antimicrobial Agents and Chemotherapy asks that you “define all abbreviations that are not used in the text”. Magnetic Resonance Imaging states that “Abbreviations and acronyms should be spelled out the first time they are used in the manuscript; less common ones should also be spelled out in tables and figures”, which suggests that well-known abbreviations used in tables and figures do not need to be explained. As always, consult the author instructions page of the target journal. If no guidance is given, then only define those abbreviations not used in the text.

Other

The journal may state in the author instructions page that a list of abbreviations, generally alphabetical, is required. This can also be seen by consulting some recent papers from the target journal. In the text itself, while the convention is to first use the full term and follow it with the abbreviation in parentheses [i.e., “bone mineral density (BMD)”], this order can be reversed for some terms that are more commonly known by their abbreviations [e.g., “TUNEL (terminal deoxynucleotidyl transferase dUTP nick end labeling)” and “MALDI-TOF (matrix-assisted laser desorption/ionization-time of flight)”].