It is most common to use a parenthetical sentence within a larger sentence.
- Do not capitalize the first letter of the parenthetical, unless it is a proper noun or proper adjective.
- Do not include a period at the end of the parenthetical sentence.
- If a parenthetical sentence ends in a question mark or exclamation mark, include it inside the parentheses or dashes. These types of punctuation are necessary in expressing the intended meaning of the parenthetical sentence.
- Be sure that punctuation for the larger sentence is not placed within the parentheses or dashes.
Ex: I thought I lost my dog (her leash broke when I was walking her), but I found her in the backyard.
Ex: The soccer team won (can you believe that?) by five goals in the second half alone.
Ex: The protesters waved their banners higher -- by this time, they had gotten media attention -- and began to march to the center of town.
You may find that a paragraph flows better if you use a parenthetical sentence within a paragraph or as a short paragraph by itself.
- Capitalize the first word as if it were a normal sentence.
- Include all punctuation within the parentheses.
- Only use parentheses. Dashes cannot be used independently.
Ex: By the first third of the book, the protagonist had left her home country. (This is when the story stops making logical sense.)
(See reference # 1)
Use parenthetical sentences sparingly since they can disrupt the flow of a sentence and distract the reader. If the information can be conveyed as a normal sentence, this is usually a better option. However, parenthetical sentences are still be very useful for providing incidental information in an efficient way.
Parentheses tend to de-emphasize information. Dashes, on the other hand, tend to call attention and place more emphasis on information. Also, if you are writing an academic paper, your teacher may have a preference towards one over the other or discourage the use of either.