更衣室

1. Origins, structure, and basic meaning

• Structure: 更衣室 (こういしつ) is a compound noun for a room provided for changing clothes.
• Basic usage: 更衣室で着替える marks the place used to change before exercise, while 更衣室のロッカー modifies storage equipment located inside that room.

2. Common pitfalls and similar expressions

• Activity room and contained fixture
  • 更衣室で marks the changing location, while the head noun in 更衣室のロッカー is the locker. The fixture itself is not called a changing room.