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APA Formatting and Style (7th ed.) for Student Papers

NAU Guide to APA

Basic Style Guidelines

1. The plural of many abbreviations and statistical symbols are formed by adding a lowercase "s," without an apostrophe: 

Examples: vols. (volumes), adjs. (adjectives), CIs (confidence intervals)
Exception: Do not add an "s" to pluralize units of measurement: 5 m (not 5 ms)
(American Psychological Association [APA], 2020, p. 173).
2. The plural of acronyms (abbreviations formed by the first letters of several words) are formed by adding a lowercase "s," without an apostrophe.
Example: BFFs : best friends forever
Other examples: URLs, CDs, lasers
(APA, 2020, p. 173)
3. The plurals of numbers are formed by adding "s" or "es," without an apostrophe:
Examples: 50s and 60s, the 1990s
I'm at sixes and sevens over the new tax rules.  (In other words, I'm very confused about the tax rules.)
(APA, 2020, p. 181)
Reference: American Psychological Association. (2020). Publication manual of the American Psychological Association 
    (7th ed.).
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