noun
underworld; world after death; realm of the dead
Refers to the afterlife or the world of the dead, often in a spiritual or mythological context. Not a common everyday word; more literary or conceptual.
彼は死界からの使者だと名乗った。
He claimed to be a messenger from the underworld.
この物語では、主人公が死界を旅する。
In this story, the protagonist travels through the world after death.
noun
blind spot; dead space; area outside one's field of vision
Used in a more technical or figurative sense to describe a place that cannot be seen or is hidden from view. The kanji 死 (death) here implies an absence of perception, not literal death.
監視カメラの死界を確認する。
Check the blind spots of the surveillance cameras.
この部屋は電波の死界になっている。
This room is a dead zone for radio waves.
Compound of 死 (death) and 界 (world, realm). The exact origin is uncertain; it appears to be a coined term used in literary or technical contexts rather than a traditional word.