noun which may take the genitive case particle 'no', noun
open to all; anyone can join
Describes an event or activity where participation is unrestricted; anyone may take part.
このイベントは参加自由です。
This event is open to everyone.
noun which may take the genitive case particle 'no', noun
optional; not compulsory
Used when attendance or participation is not required; you can choose whether to take part.
会議への出席は参加自由です。
Attendance at the meeting is optional.
自由参加 also means 'free participation' but is less common than 参加自由. 参加自由 is the standard phrase for 'open to all' or 'optional'.
Compound of 参加 (participation) and 自由 (free, unrestricted).