noun
other world; spirit world; supernatural realm
Refers to a world beyond the ordinary human realm, often used in fantasy, horror, or spiritual contexts. Can imply an afterlife, a parallel dimension, or a realm of spirits and monsters.
その神社は異界への入り口と言われている。
That shrine is said to be an entrance to the other world.
彼は異界から来た怪物と戦った。
He fought a monster from another world.
Compound of 異 (i, 'different, strange') and 界 (kai, 'world, realm'). The exact historical origin is uncertain, but the word follows a common Sino-Japanese pattern for abstract realms.