| Rule 1. |
To avoid confusion, use commas to separate words and word groups with a series of three or more. |
| Example: |
My $10 million estate is to be split among my husband, daughter, son, and nephew. Omitting the comma after son would indicate that the son and nephew would have to split one-third of the estate. |
| Rule 2. |
Use a comma to separate two adjectives when the word and can be inserted between them. |
| Examples: |
He is a strong, healthy man. |
| We stayed at an expensive summer resort. You would not say expensive and summer resort, so no comma. |
|
| Rule 3. |
Use a comma when an -ly adjective is used with other adjectives. |
| NOTE: |
To test whether an -ly word is an adjective, see if it can be used alone with the noun. If it can, use the comma. |
| Examples: |
Felix was a lonely, young boy. |
| I get headaches in brightly lit rooms. Brightly is not an adjective because it cannot be used alone with rooms; therefore, no comma is used between brightly and lit. |
|
| Rule 4. |
Use commas before or surrounding the name or title of a person directly addressed. |
| Examples: |
Will you, Aisha, do that assignment for me? |
| Yes, Doctor, I will. |
| NOTE: |
Capitalize a title when directly addressing someone. |
|
Source: http://www.grammarbook.com/punctuation/commas.asp
