noun
application to participate; registration
Used for signing up for events, courses, conferences, etc. Often appears in formal contexts.
セミナーの参加申し込みは締め切りました。
Registration for the seminar has closed.
参加申し込みフォームに必要事項を記入してください。
Please fill in the required information on the participation application form.
Compound of 参加 (participation) and 申し込み (application).