English and ESL Instructor
A parenthesis (plural: parentheses) is any set of words or any statement that provides additional explanation for a sentence, but is not part of the subject, verb, nor complement. A conventional sentence follows the subject-verb-complement format:
James is an engineer.
In the above sentence, the subject is James, the verb is is, and the complement is an engineer. If we want to give more information about who James is in this sentence, then we would write that in parenthesis:
James, a close friend of mine, is an engineer.
In the above example, a close friend of mine would be a parenthetical statement. Notice that there are now commas in the sentence to indicate parenthesis.
A parenthesis can also appear at the beginning or end of a sentence:
A former gang member, Ken now works to keep youth away from gangs. (The parenthesis is at the beginning.)
Kobe Bryant has 33,643 total career points, the third most of all-time in the NBA. (The parenthesis is at the end.)
Regardless of where the parenthesis is, the comma is the punctuation mark that indicates its presence.