誓い

1. Origins, structure, and basic meaning

• Structure: 誓い is a noun read ちかい, meaning an oath or vow to do or uphold something.
• Basic usage: Use 誓いを立てる for making a vow and …という誓い for stating its content.
  • 選手たちは来年こそ優勝すると誓いを立てた。 describes the players vowing to win next year; 約束を守るという誓いを、彼は最後まで忘れなかった。 says that he never forgot the vow to keep the promise.

2. Common pitfalls and similar expressions

• 誓いを立てる
  • を立てる forms the expression for making a firm vow.
• …という誓い
  • という presents the preceding clause as the content of the vow.
• 誓い and 約束
  • 約束 is a promise generally, while 誓い emphasizes a firm commitment to uphold it.