Section 15.6 The Comma
The comma is the most frequently used—and misused—punctuation mark. Section 15.3 covered commas at sentence boundaries (compound sentences, introductory clauses). This section covers the remaining comma rules, all of which operate within a single clause rather than between clauses.
After Introductory Elements.
Use a comma after introductory words, phrases, or short modifiers that precede the main clause:
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However, I disagree. (conjunctive adverb)
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After the meeting, we went to lunch. (prepositional phrase)
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Running quickly, she caught the bus. (participial phrase)
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Frankly, I’m not interested. (sentence-level adverbial)
Very short introductory elements (one or two words) may omit the comma in open-punctuation styles: Today we leave. But in close punctuation and academic writing, the comma is preferred: Today, we leave.
Commas with Nonrestrictive Elements.
In Chapter 13 you learned the distinction between restrictive and nonrestrictive modifiers. Commas signal to the reader that a modifier is nonrestrictive—adding extra information rather than identifying which one:
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My sister, who lives in Boston, is visiting. (nonrestrictive—one sister)
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The report, which I submitted yesterday, was approved. (nonrestrictive—report already identified)
Do not use commas with restrictive modifiers:
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The students who studied passed. (restrictive—identifies which students)
Commas in Series.
Separate items in a list of three or more:
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She bought apples, oranges, and bananas.
The comma before and (the Oxford comma) is optional but recommended for clarity:
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I admire my parents, Gandhi, and Mother Teresa. (clear)
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I admire my parents, Gandhi and Mother Teresa. (ambiguous—are the parents Gandhi and Mother Teresa?)
Commas with Coordinate Adjectives.
Separate adjectives that independently modify the noun:
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a tall, elegant woman (tall and elegant each modify woman independently)
Test: If you can put and between them and the meaning holds, use a comma.
Do not use commas between cumulative adjectives (adjectives that build on each other in the fixed order from Chapter 13):
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a big red barn (not
big, red barn—big modifies red barn as a unit)
Comma Misuse: Separating Subject from Verb.
Never place a comma between a subject and its verb, even when the subject is long:
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The man who arrived late, was my cousin. -
Correct: The man who arrived late was my cousin.
