noun
participation fee; entrance fee; registration fee
Fee required to participate in an event, course, or activity. Often used for conferences, workshops, tours, and classes.
セミナーの参加費は無料です。
The seminar participation fee is free.
参加費を事前に振り込んでください。
Please transfer the participation fee in advance.
会費 is a membership fee or dues for belonging to an organization, whereas 参加費 is a one-time or per-event participation cost.
Compound of 参加 (participation) + 費 (expense, cost).