必須

1. Origins, structure, and basic meaning

• Structure: Spelling: 必須. Reading: ひっす. Core meaning: required; mandatory.
• Basic usage: Representative examples: 受付では身分証明書の提示が必須です / この授業では、最終レポートの提出が必須になっている.

2. Common pitfalls and similar expressions

• Required versus important
  • 必須 means required by a condition or rule. 重要 only means important and does not by itself create an obligation, so the two should be distinguished.