when to use a comma
Rule 2. Use a comma to separate two adjectives when the order of the adjectives is interchangeable. Example: He is a strong, healthy man. We could also say healthy, strong man. Example: We stayed at an expensive summer resort. We would not say summer expensive resort, so no comma.
Commas and periods are the most frequently used punctuation marks. Commas customarily indicate a brief pause; they're not as final as periods. Rule 1. Use commas to separate words and word groups in a simple series of three or more items. Example: My estate goes to my husband, son, daughter-in-law, and nephew. Note: When the last comma in a series comes before and or or (after daughter-in-law in the above example), it is known as the Oxford comma.
Quick Guide to Commas. 1. Use commas to separate independent clauses when they are joined by any of these seven coordinating conjunctions: and, but, for, or, nor, so, yet. 2. Use commas after introductory a) clauses, b) phrases, or c) words that come before the main clause.