noun
article left behind; lost property; specimens
Formal term used in legal, forensic, or official contexts for items left behind at a scene, after death, or as evidence. Also used for specimens or samples in certain technical settings.
警察は現場に残された遺留物を詳しく調べた。
The police carefully examined the articles left behind at the scene.
遺留物から被害者の身元が判
The victim's identity was determined from the belongings left behind.
忘れ物 is a common, everyday word for something accidentally left behind, whereas 遺留物 is a formal term used in official or investigative contexts.
Compound of 遺留 (iryū, 'leaving behind') + 物 (butsu, 'thing'). The exact historical derivation is uncertain, but the word is used in modern formal Japanese.