1. A clause inserted in a sentence, which is grammatically complete without it, for explanation, confirmation, &c., and indicated thus.

Nuttall's Standard dictionary of the English language By Nuttall, P.Austin

• paranthesis,
• parenthses,
• paresthesias,
• parenthese,
• parentisis,
• parethesis,
• parenthsis,
• paraentheses,
• parenthasis,
• peranthesis,
• prenthasis,
• parenthisis,
• parenthasys,
• perenthesis,
• paretheses,
• parenthises,
• parenthesesis,
• parenthesees,
• parenthesies,
• parenteses

• parented,
• parenthetic,
• parentless,
• parenthetical,
• parentage,
• parenteau,
• parental,
• parenthood.

The adjective form of the word "parenthesis" is "parenthetical".

The plural of the "parenthesis" can be the "parentheses".

The singular of the "parenthesis" can be the "parenthesis".