Originally (chiefly Printing): a square bracket; the use of square brackets; (also) the word, clause, or phrase inserted within such brackets. In later use more generally: a parenthesis or (treated as plural) a pair of parentheses.
The placing of a word or phrase beside, or in syntactic parallelism with, another; the juxtaposition of two or more grammatically parallel words or phrases (as in our friend the doctor); = "apposition".