A clause that adds identifying information or restricts the noun to a specific group or lot does not use commas. A clause that adds extra information is set off with commas (parentheses or dashes.)
| BY |
METHODS OF IDENTIFICATION |
WITH AN "EXTRA" NON-IDENTIFYING CLAUSE |
| |
no comma |
use a comma when adding a non-identifying clause |
| (none) |
The store sells organic produce. (unidentified) |
|
| a clause |
The store where I shop sells organic produce. |
|
| a phrase |
The store on the corner of Channing and University sells organic produce. |
The store on the corner of Channing and University, where I shop, sells organic produce. |
| a name |
Whole Foods sells organic
produce. |
Whole Foods, where I shop, sells organic
produce. |
| later mention |
The store that sells organic produce is Whole Foods. |
The store selling organic produce, where I shop, is Whole Foods. |
| earlier mention |
I like Whole Foods. The store sells organic produce. |
I like Whole Foods. The store, where I shop, sells organic produce. |
| referring to all |
Organic food stores sell organic produce. |
Organic food stores, where I shop, sell organic produce. |
| uniqueness |
The moon is bright. |
The moon,
which is full tonight, is bright. |