This is the 7499th most frequent Japanese word.
入団
"入団" means "joining a group or organization, especially a team or club."
The term "入団" here refers to formally becoming a member of a sports team.
彼はプロ野球チームに入団しました。
He joined a professional baseball team.
In this context, "入団" is used to denote the action of integrating into an organization or a group.
新しいメンバーとして団体に入団することを決意しました。
He decided to join the organization as a new member.
"入団" signifies the prior action of becoming part of an organization, leading to planning post-membership.