In rhetoric, a parenthesis
( plural: parentheses;
from the Greek word
which comes in turn from words meaning
"alongside of" and "to place" )
or parenthetical phrase
is an explanatory or qualifying
word, clause, or sentence
inserted into a passage.
The parenthesis could be left out
and still form
grammatically correct text.
Parentheses are usually marked off
by round or square brackets