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Punctuation
Ruled slips filed under Punctuation.
Punctuation§
When a Comma Changes the Meaning of a Sentence
CorrectPlace a comma before the coordinating conjunction (and, but, for, nor, or, so, yet) when it links two independent clauses; do not use a comma when the conjunction links two verbs, nouns, phrases, or dependent clauses that share a subject.
Common errorWriters often insert a comma before every and or but, even when the conjunction joins compound verbs, objects, or phrases rather than independent clauses.
ExceptionA comma may be omitted before a coordinating conjunction between short independent clauses (usually under five words each) if the sentence remains clear; a comma is also required when the conjunction could be misread as joining only the last two items in a series.
The comma before a coordinating conjunction is not a decorative pause.
Punctuation§
Why the Serial Comma Debate Never Really Ends
CorrectPlace a comma immediately before the conjunction that joins the final two elements of a series of three or more: red, white, and blue.
Common errorDropping the final comma and leaving the last two items fused, as in red, white and blue, which can imply a pair rather than three separate items.
ExceptionOmit the serial comma when the final element is a single word tightly bound to the preceding one, when a style guide mandates omission, or when the series is only two items.
The serial comma, sometimes called the Oxford comma, is the comma placed before the coordinating conjunction in a series of three or more items.
Punctuation§
Dashes: Telling an En Dash from an Em Dash
CorrectEm dash: no spaces around it in AP style. En dash: no spaces around it in ranges and compounds.
Common errorUsing a hyphen or en dash where an em dash is needed, or spacing the em dash.
ExceptionIn some publishing systems or when a font lacks an em dash, a spaced en dash may stand in for an em dash, but AP style prefers the em dash.
The em dash is the long dash that signals a break in thought, an aside, or an abrupt change in a sentence.
Punctuation§
The Semicolon: When a Period Would Be Better
CorrectPlace a semicolon between two independent clauses that are closely related in meaning and not joined by a coordinating conjunction (and, but, or, nor, for, so, yet).
Common errorUsing a semicolon where a period or a comma plus conjunction is needed, especially when the clauses are not closely related or when the second clause is not independent.
ExceptionA semicolon may be used to separate items in a complex list when the items themselves contain commas, even if the items are not independent clauses.
The semicolon is a mark of connection.