1. Left to one's wish or choice; leaving something to choice.

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

• optinal,
• opptional,
• opitonal,
• emtional,
• oditional,
• eomtional,
• opticial,
• optioal,
• optiona,
• attional,
• ational,
• ocational,
• optionaly,
• opertional,
• optoinal,
• optial,
• opitional,
• optionable,
• adtional,
• optioanl

• ophiodon,
• optimism,
• optimize,
• optimist,
• optimally,
• optimal,
• optionally,
• option,
• optimise.

The adjective form of the word "optional" is "optional".

The plural form of "optional" is "optionals".

The singular form of the word "optional" is "option"