Purpose
By the end of this lesson, you will be able to correctly apply the core rules of comma usage, including the most commonly disputed cases.Lesson Explanation
This lesson consolidates comma rules already previewed throughout the course into one systematic reference. Compound sentences (Part 2, Lesson 2): a comma goes before a coordinating conjunction joining two independent clauses: “I wanted to go, but it was raining.” Introductory dependent clauses (Part 2, Lesson 3): a comma follows a dependent clause that comes first: “Although it was raining, I went for a walk.” Non-restrictive clauses (Part 2, Lesson 4): commas set off non-essential descriptive information: “My neighbor’s dog, which barked all night, kept me awake.” Serial (list) commas separate three or more items in a list: “I bought apples, oranges, and bananas.” A genuinely disputed case is the Oxford comma — the comma before the final “and”/”or” in a list. Both including and omitting it are considered correct depending on style guide, but including it can prevent genuine ambiguity: “I invited my parents, the president, and the vice president” (three groups, if the Oxford comma is used) versus the genuinely ambiguous “I invited my parents, the president and the vice president” (which could imply the parents ARE the president and vice president, without the final comma). Introductory words/phrases also typically take a comma: “However, she disagreed.” “In the morning, we left.”Practice Questions
1. Where does a comma go relative to a coordinating conjunction joining two independent clauses?
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Before it.2. Write “I wanted to go, but it was raining” — what earlier lesson covers this rule?
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Part 2, Lesson 2.3. When a dependent clause comes first, is a comma required after it?
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Yes.4. What earlier lesson covers introductory dependent clauses?
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Part 2, Lesson 3.5. Are non-restrictive clauses set off with commas?
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Yes.6. What earlier lesson covers restrictive vs. non-restrictive clauses?
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Part 2, Lesson 4.7. What is a serial (list) comma used for?
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Separating three or more items in a list.8. What is the Oxford comma?
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The comma before the final “and”/”or” in a list.9. Is including or omitting the Oxford comma always correct or always incorrect?
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Neither — both are considered correct depending on style guide.10. How can the Oxford comma prevent ambiguity, per the parents/president example?
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It clarifies that the parents, the president, and the vice president are three separate groups, not that the parents are the president and vice president.11. Does an introductory word like “However” typically take a comma?
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Yes.12. Write an example sentence with an introductory phrase followed by a comma.