早退

1. Origins, structure, and basic meaning

• Structure: 早退 (そうたい) is an action noun, used with する, for leaving school or work before the scheduled end.
• Basic usage: 学校を早退した reports leaving school early because of illness, while 早退する前 locates telling a supervisor before an early departure from work.

2. Common pitfalls and similar expressions

• Departure point marked by を
  • In 学校を早退する, を marks the place departed rather than an object being changed. The workplace context in the second example also shows that the action is not limited to school.