Punctuation: Dashes and Parentheses Usage

Study Notes

Use parentheses to indicate alternative terms (as in form letters).
Use parentheses to enclose abbreviations synonymous with spelled-out forms, occurring after the forms or if the order is reversed.
Use parentheses to enclose Arabic numerals, which confirm written numbers.
Use parentheses to mark numbered or lettered divisions within sentences or paragraphs.
Use parentheses to set off supplementary, parenthetic, or explanatory material that does not change the meaning of the main sentence.

The dash can show a break in thought or sentence structure. Example: He had tried to change--you're not even paying attention!
Another function of dashes is to emphasize parenthetical material. Example: Tomorrow--how I fear it!--is the big test.
The dash can also be used to indicate a summarizing clause. Example: The house, the yard, the garage--they had remained untouched.

Parentheses can be used to indicate alternative terms. Example: You may study any lesson(s) on our site.
Parentheses can also be used to enclose abbreviations synonymous with spelled-out forms occurring after the forms, or if the order is reversed. Example: I will meet with U.E.A. (Utah Education Association) leaders at 4:00.
Parentheses are also used to enclose Arabic numerals, which confirm written numbers. Example: They will arrive in (30) thirty days.
Parentheses can be used to mark numbered or lettered divisions within sentences or paragraphs. Example: We will read the following chapters for our discussion tomorrow: (1) Africa, (2) India, (3) Iceland.
Finally, parentheses are used to set off supplementary, parenthetic, or explanatory material that does not change the meaning of the main sentence. Example: Joe Jones (you knew him) visited me yesterday.