遺書|いしょisho[1]atamadaka (head-high)

1. nounnote left by a dead person; suicide note; testamentary letter; will; testament
   叔父おじは去年きょねん遺書いしょを作つくった。↗

   My uncle made a will last year.
2. nounposthumous work

• Synonym遺言書ゆいごんしょNeutralA will document setting out who inherits what, drawn up with legal validity in mind; 「遺書」 can be nothing more than words left for one's family.
• Synonym遺言状ゆいごんじょうWrittenSame meaning as 「遺言書」—a document recording a will—but the term is older; 「遺書」 does not necessarily involve disposing of property. Written/formal.
• Related書き置きかきおきNeutralA note left for someone when you go away — it need not involve death at all, unlike 「遺書」, which is a letter the deceased wrote before dying.

For a letter or note written before death for those left behind, 「遺書」 is the word. Use 「書き置き」 for a note left when going away, and 「遺言書」 (or the older 「遺言状」) for a legally binding will on property.

Usage comparisons are AI-assisted and cross-checked by multiple models; for study reference only

1. 死しぬ前まえに本人ほんにんが書き残かきのこした手紙てがみや文書ぶんしょ。
2. 死後しごに出版しゅっぱんされた著作ちょさくや作品さくひん。