English Grammar for the Utterly Confused - Laurie Rozakis 2003
Parentheses
Chapter 10 Punctuation
Part 4 A Writers Tools
Use parentheses to set off nonessential information. In essence, the information in the parentheses is a nonessential modifier because it gives the reader additional information that is not crucial.
1. Use parentheses to enclose additional information in a sentence.
Capitalize all proper nouns and proper adjectives (see Chapter 11).
2. Use parentheses to enclose numbers or letters.
To prepare spaghetti, follow these steps in order: (1) Bring a pot of lightly salted water to boil; (2) add pasta; (3) cook about 10 minutes, to taste.