Brief Overview of PunctuationThis webpage from Purdue OWL sets out when and how to use commas, sermi-colons, parenthesis, a dash, quotation marks, and italics.
Grammar and PunctuationGrammar and punctuation tools from the University of Wisconsin-Madison's Writing Center's Writer's Handbook.
AbbreviationsPurdue OWL sets out the rules for using abbreviations when writing and citing using APA 7th edition, including how to form the plural of abbreviations.
Numbers and StatisticsPurdue Owl sets out the rules for using numbers and statistics when writing and citing using APA 7th edition, including how to form the plural of numbers.
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.). https://doi.org/10.1037/0000165-000)
