Parenthesis is singular, parentheses is plural. One parenthesis, two parentheses. Like crisis/crises, axis/axes.
but, parentheses always comes in pairs.
if not someone needs to be executed
You might want to refer to the left parenthesis or the right parenthesis and then it would be incorrect to use the plural.
The lighter side of ADHD
Parenthesis is singular, parentheses is plural. One parenthesis, two parentheses. Like crisis/crises, axis/axes.
but, parentheses always comes in pairs.
if not someone needs to be executed
You might want to refer to the left parenthesis or the right parenthesis and then it would be incorrect to use the plural.