加入

1. Origins, structure, and basic meaning

• Structure: 加入 is read as かにゅう and is a noun and する verb for formally joining an organization, insurance plan, system, or similar arrangement.
• Basic usage: Enrolling in a new insurance plan appears in 保険に加入する, while membership requirements for a union appear in 組合への加入条件.

2. Common pitfalls and similar expressions

• Entering a membership or coverage relationship
  • It more strongly suggests becoming a member or entering continuing coverage than attending one event.
• Difference from 参加
  • Unlike the broad word for taking part in a meeting, event, or activity, this term readily denotes entering an ongoing relationship through enrollment.