More APA Style Guidelines:

Abbreviations

Using abbreviations can be an effective way to avoid repeating lengthy, technical terms throughout a piece of writing, but they should be used sparingly to prevent your text from becoming difficult to read.

Many abbreviations take the forms of acronyms (abbreviations consisting of the first letter of each word in a phrase and pronounced as a word) and initialisms (abbreviations consisting of the first letter of each word in a phrase and pronounced letter by letter). An example of an acronym is NIMH (standing for "National Institute of Mental Health"). An example of an initialism is BBB (standing for "Better Business Bureau"). Note that acronyms and initialisms generally use all capital letters, and there are no periods between the letters.

To use an abbreviation, write out the term or phrase on first use, followed by the abbreviation in parentheses. Use brackets if introducing an abbreviation inside parentheses. See these examples:

The patient had been diagnosed with traumatic brain injury (TBI) in March of the previous year.

Walden students need to know how to cite information using the American Psychological Association (APA) guidelines.

Crime increased 20% in the study area during this time (Federal Bureau of Investigation [FBI], 2019).

After introducing the abbreviation, use the abbreviation by itself, without parentheses, throughout the rest of the document.

The patient had been diagnosed with traumatic brain injury (TBI) in March of 2014. According to the Centers for Disease Control and Prevention (CDC, 2015), people with TBI often have difficulty with memory and concentration, physical symptoms such as headaches, emotional symptoms such as sadness and irritability, and difficulty falling asleep. Although the patient explained that she experienced frequent headaches and difficulty concentrating, she had not been regularly taking any medication for her TBI symptoms when she visited the clinic 6 months after her diagnosis.

Note: When introducing an abbreviation within a narrative citation, use a comma between the abbreviation and the year.

Simply add an “s” to an abbreviation to make it plural. (Do not add an apostrophe.)

I work with five other RNs during a typical shift.

Note: RN is a commonly used acronym found in Merriam-Webster’s Dictionary, so it does not need to be introduced. See the “Exceptions to the Rules” section below for more information about commonly used abbreviations.

There are a few exceptions to the basic rules:

• If you use the phrase three times or fewer, it should be written out every time.
• Commonly used acronyms and abbreviations may not need to be written out. If an abbreviation appears as a noun in Merriam-Webster’s Collegiate Dictionary, then it does not need to be written it out on first use. Examples include words such as IQ, REM, and HIV.
• Other than abbreviations prescribed by APA in reference list elements (e.g., “ed.” for “edition,” “n.d.” for “no date,” etc.), do not use abbreviations in the references list. For example, a source authored by the Centers for Disease Control and Prevention would not be abbreviated as CDC in the references list. Abbreviations should also not be used in headings, table titles, and figure captions.
• If using an abbreviation for a unit of measure with a numerical value, you do not need to write the term out on first use. For example, instead of writing “12 grams;” you can simply use “12 g.” If, however, you use a unit of measure without a numerical value, write the term out (e.g., “several grams”).

In APA style, "United States: should always be spelled out when it is used as a noun or location.

Example: In the United States, 67% reported this experience.

"United States" should be abbreviated as "U.S." when it is used as an adjective.

Examples: U.S. population and U.S. Census Bureau.