|Definition - The name for the () symbols when they are used to enclose material that can be omitted from a sentence without making the sentence grammatically incorrect.|
1. Use them to enclose information that clarifies the preceding text.
He said he expected to be paid 800 smackers ($800).
2. Use them to add supplementary information.
Senator Scoop Jackson (Democrat, Boeing) spoke for hours.
3. The punctuation inside the parentheses is independent of the rest of the text.
A man named Bob Loblaw (Yes, that was his name!) was my pronunciation coach.
4. Use them to enclose asides.
I promised I would pay him ASAP (not!).
5. Use full parentheses to enclose list numbers.
We need someone who can (1) tell the truth, (2) get things done, and (3) not leave a mess.
6. Put periods inside the parentheses only if the entire sentence is inside the parentheses.
Please read the afterword (It is attached as Appendix A.).
7. Use the them to indicate "both singular or plural."
Why don't you state the problem(s)?
8. Don't nest parentheses within parentheses. It's confusing. If you must do this, use different types of brackets.
This is an example (It's a good example [It shows you how to nest properly.] of this phenomenon.) of how to nest properly.
9. Use them to encase either an abbreviation or an acronym that follows the complete term.
The Ministry of Stuff We Don't Know (SWDK) is having an official meeting today.
Etymology - The word derives via Middle French and Late Latin from the Greek parenthesis, which literally means "a putting in beside" (from para, beside + en, in + tithenai, place).
The term was extended to denote the curved brackets by 1715. Prior to this, Erasmus had named them the lunula, because they reminded him of the moon; e.g. ().
Oxford English Dictionary - Its first citation in its punctuation-symbol sense is from 1715:
"Our old Bibles … had these Words … in small Letters, and sometimes in a Parenthesis."
( in Somers Tracts II. 436 )