120 Double Punctuation (English)

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Understanding Double Punctuation

Double punctuation should be avoided if possible, but in some cases are necessary. A period or comma always go inside a quotation mark, so that is an example of double punctuation, a period followed by a quote mark.
When using Latin abbreviations; e.g., mid-sentence, a comma follows the Latin text if a non-restrictive expression follows; otherwise, it ends with a period and the sentence continues on without any additional punctuation nor without any capitalization following that period.
When a term is placed inside of quotes that are inside parentheses, then the author is introducing an abbreviation, acronym, or nickname of the noun directly preceding it. The same punctuation can never follow itself a duplicate instance; for example, two commas can never follow each other; they must always be surrounding some form of text, and two periods can never follow each other; an ellipsis is three periods.
Same applies to any other punctuation mark with one exception: parentheses, brackets, or curly braces. Parentheses may be double nested inside each other. In computer help manuals circa 1970s, double colons were used to separate subjects of nested help manual pages.