Translation guide
The English word "optional" means something is not required and can be chosen freely. In Japanese, this concept is expressed through adjectives, nouns, and set phrases that indicate choice, non-compulsion, or the ability to do without.
Describing something (a feature, item, action) that is available but not mandatory.
A formal noun/adjective meaning 'optional', 'voluntary', or 'at one's discretion'. Common in official contexts, forms, and technical settings.
Participation is optional.
Please fill in the optional fields.
A casual phrase meaning 'it's okay not to have/do'. Very common in everyday speech for saying something is optional.
An umbrella is optional (you don't need one).
A reply is optional.
A slightly more formal version of なくてもいい, meaning 'it doesn't matter if you don't have/do'. Polite and common in service situations.
A reservation is optional.
Loanword from English, used for optional extras, features, or choices, especially in products, services, and technology.
This feature is optional.
You can add insurance as an option.
Literally 'choice system', used for systems where something is optional, like elective courses or optional benefits.
This subject is optional.
Referring to add-ons, accessories, or features that cost extra or are not part of the standard package.
任意 is a formal, written term often used in documents, forms, and rules. オプション is a casual loanword common in everyday conversation about products and services. For 'you don't have to', use なくてもいい in casual speech.
Filling this out is optional.
You can add dessert as an option.
随意 (ずいい) means 'optional' in legal or very formal contexts, but it's rare and can sound unnatural. Stick to 任意 or オプション for most situations.
サンルーフはオプションです。
The sunroof is optional.