1. To separate introductory phrases from the main sentence: While running across the park, Jeremiah thought his lungs would burst.
2. To separate two independent clauses: Rosa double-checked her watch, and they boarded the train. OR Ryan hit the baseball almost to the warning track, but Diego caught it in fair territory.
3. When opening a sentence with a gerund used to describe action by the subject: Grinning, the earl nodded. OR Breathing hard, she flopped down on the grass. NOT Shimmering sunlight tipped the blades of grass with gold.
4. To break out description of a subject: Dirt-streaked and sweaty, Bob longed for a shower. OR Bob, dirt-streaked and sweaty, longed for a shower.
5. To separate dialogue or any quotation from its tag: “You don’t know me that well,” Emma purred. OR Boy George said Madonna was, “a gay man trapped in a woman’s body.” NOTE: "I hate you." Lisa fisted her hands at her sides. does not earn a comma because there is no dialogue tag. There is an action performed by Lisa. Dialogue tags are words like said, replied, shouted, retorted, asked or exclaimed.
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