使用済み

1. Origins, structure, and basic meaning

• Structure: The spelling is 使用済み, read しようずみ, and it combines 使用, meaning use, with 済み, meaning completed. It functions as a noun or modifier.
• Basic usage: 使用済み describes something already used or spent, with its intended use completed.

2. Common pitfalls and similar expressions

• A used ticket kept and a used container collected
  • Both examples use the form 使用済み. A ticket is retained as a souvenir after use, while a finished container is placed in a designated box.
• A souvenir ticket and containers for a specified box
  • 使用済みの切符を記念に保管した。 — I kept the used ticket as a souvenir.
  • 使用済み容器はこちらの箱へ入れてください。 — Please put used containers in this box.