Cochrane Style Manual
Common abbreviations

In this section: Commonly used abbreviations | Common abbreviations that do not need to be defined | Acronyms used within Cochrane | e.g., etc., and i.e. | Currency abbreviations

Commonly used abbreviations

This table lists some abbreviations commonly used in Cochrane Reviews. See also Common abbreviations that do not need to be defined and Frequently used names.

Term Abbreviation
absolute risk reduction ARR
control group risk (avoid control event rate) CGR
controlled clinical trial CCT
confidence interval CI
degrees of freedom df
inverse variance or intravascular

Note: if both terms are abbreviated in a review, use lower case 'iv' for intravascular.

Mantel-Haenszel M-H
mean difference (avoid weighted mean difference) MD
number needed to treat for an additional harmful outcome (avoid number needed to harm) NNTH
number needed to treat for an additional beneficial outcome (avoid number needed to treat) NNTB
odds ratio OR
Peto odds ratio Peto OR
randomized controlled trial RCT
risk difference RD
risk ratio (formerly called relative risk in Review Manager 4) RR
standard deviation SD
standard error SE
standardized mean difference SMD

Common abbreviations that do not need to be defined

Also note that it is not necessary to define the full unit name of standard SI units (see General guidance on SI units in the section on Units and systems of measurement).

Term Abbreviation
United States of America USA
United Kingdom UK
Deoxyribonucleic acid DNA
Human immunodeficiency virus HIV
Acquired immune deficiency syndrome AIDS
Grading of Recommendations, Assessment, Development and Evaluation GRADE
Preferred Reporting Items for Systematic Reviews and Meta-Analyses PRISMA
Consolidated Standards of Reporting Trials CONSORT
Medical Subject Headings MeSH (not MESH or Mesh)

Acronyms used within Cochrane

A list of acronyms used within Cochrane is available in the Glossary of terms.

e.g., etc., and i.e.

e.g.: an abbreviation for ‘for example’ (from the Latin ‘exempli gratia’) that can be used in lists within the text, when examples are given in brackets, and in tables (for brevity). Use the form ‘e.g.’ with no following comma.

etc.: always write 'etc.' (followed by a full stop) in Cochrane Reviews. Use a comma before ‘etc.’ if it follows more than one item in a list. If 'etc.' is used at the end of a sentence, do not use two full-stops.

i.e.: an abbreviation for ‘that is’ (from the Latin ‘id est’) that can be used for lists within the text, when information is given in brackets, and in tables (for brevity). Use the form ‘i.e.’ with no following comma.

Correct Incorrect
e.g. (e.g. men, women, children) e.g.,
i.e. (i.e. men, women, children) i.e.,
etc. (Canada, USA, Germany, etc.) etc

Currency abbreviations

Currencies should be expressed using standard three-letter codes defined by ISO-4217, but as with other abbreviations it is generally helpful to expand on first use.

Common codes include USD (US dollar), EUR (euro), and GBP (pounds sterling). Full list:

See also: Units and systems of measurement: currencies

Section info
John Hilton (
Describe change
Added information on currency abbreviations
Change date
7 February 2019