“Parenthesis: [Stress: ‘pa-REN-the-sis,’ Plural parentheses (‘-seez’)]. 1. In grammar, a qualifying, explanatory, or appositional word, phrase, clause, or sentence that interrupts a construction without otherwise affecting it. A written or printed parenthesis may be marked by pairs of commas, dashes, or round brackets/parentheses: Our new manager (he has just this minute arrived) would like to meet you. A spoken parentheses has the same intonation as an aside. 2. In the plural, a name for round brackets: the general term in American English, but a less common, more technical term in British English (short form parens).”
Excerpted from: McArthur, Tom. The Oxford Concise Companion to the English Language. New York: Oxford University Press, 2005.