共催

1. Origins, structure, and basic meaning

• Structure: 共催 (きょうさい) denotes jointly hosting or sponsoring an event.
• Basic usage: 図書館と学校が共催した coordinates two hosts; 町による共催 names cohosting carried out by towns.

2. Common pitfalls and similar expressions

• Shared hosting responsibility
  • 共催 means that two or more organizations jointly host an event and share responsibility for its operation. It is distinct from merely sponsoring or assisting.