Parentheses (like these) are used for two main reasons.In general writing:
In APA style guidelines:
To show that the information in the parentheses is less important than the information that is not in parentheses.
Warning: Do not overuse parentheses. In academic writing, it is usually best to show the relative importance of information by your wording. If something is not important enough to express normally in the text, consider carefully whether you should just leave it out completely.
The authors' names and the reference's copyright date, along with the page number if quoting directly, are enclosed in parentheses. The parentheses can occur anywhere in the sentence.
Smith (2008) confirmed the fact that residential treatment is more effective.
Punctuation Tip: When the source is cited at the end of the sentence, the period goes after the parenthesis.
Residential treatment has been found to be more effective (Smith, 2008).
According to Smith (2008), "Residential treatment for all segments of the population has been found to be vastly more effective than outpatient treatment"(p. 205).