Most abbreviations must be defined (explained) in an APA Style paper upon first use. However, it is also important to consider overall level of use of abbreviations in a paper to ensure you are using neither too many nor too few abbreviations.

Level of Use

Avoid both the overuse and underuse of abbreviations. If you abbreviate a term, use the abbreviation at least three times in a paper. If you use the abbreviation only one or two times, readers may have difficulty remembering what it means, so writing the term out each time aids comprehension. However, a standard abbreviation for a long, familiar term is clearer and more concise even if it is used fewer than three times. This case is an exception to the guideline to use an abbreviation at least three times in a paper if you use it at all.

Definition of abbreviation is covered in Section 6.25 of the APA Publication Manual, Seventh Edition

How to Define an Abbreviation in the Text

When you first use a term that you want to abbreviate in the text, present both the full version of the term and the abbreviation. The following guidance applies to the definition of any kind of abbreviation, including the abbreviation for a group author.

  • When the full version of a term first appears in a sentence in the text, place the abbreviation in parentheses after it.

posttraumatic stress disorder (PTSD)
  • When the full version of a term first appears in parenthetical text, place the abbreviation in square brackets after it. Do not use nested parentheses.

(i.e., posttraumatic stress disorder [PTSD])
  • If a citation accompanies an abbreviation, include the citation after the abbreviation, separated with a semicolon. Do not use nested or back-to-back parentheses.

Narrative format: Clinician-Administered PTSD Scale for DSM-5 (CAPS-5; Weathers et al., 2018)
Parenthetical format: (Clinician-Administered PTSD Scale for DSM-5 [CAPS-5]; Weathers et al., 2018)
  • When the full version of a term appears for the first time in a heading, do not define the abbreviation in the heading; instead define the abbreviation when the full version next appears. Use abbreviations in headings only if the abbreviations have been previously defined in the text or if they are listed as terms in the dictionary.

  • If an abbreviation has appeared in the abstract as well as the text, define it on first use in both places.

  • After you define an abbreviation, use only the abbreviation. Do not alternate between spelling out the term and abbreviating it.

Abbreviations to Use Without Definition

Some kinds of abbreviations do not need to be defined or explained in an APA Style paper because they are so common that readers are sure to be familiar with them.

Do not define the following kinds of abbreviations:

  • abbreviations listed as terms in the dictionary (e.g., AIDS, IQ)
  • measurement abbreviations (e.g., kg, cm)
  • time abbreviations used with numerical values (e.g., 5 hr, 30 min)
  • Latin abbreviations (et al., i.e., e.g., etc.)
  • many statistical abbreviations (M, SD, SE, t, etc.)

Define all other abbreviations. Although some may be familiar to your readers (e.g., “RT” for reaction time or “ANOVA” for analysis of variance), other readers not familiar with these terms will benefit from having the abbreviations explained.