Yokai can be written using other Chinese characters, 夭怪, and words such as yo, oni, obake (ghost), kaii (mysterious creature), kaibutsu (monster), kesho (reincarnated or transformed being), chimimoryo (evil spirits of mountains and rivers), tsukimono (something that possesses people or things), bake (ghost), bakemono (ghost), hyakki (hundred demons), henge (apparition), ma (devil), mamono (devil), mononoke (specter), mononoke, youi, yokaihenge (specter) are also used with a similar meaning.
夭怪とも表記し、妖（夭）・鬼・お化け・怪異・怪物・化生・魑魅魍魎（ちみもうりょう）・憑き物・化け・化け物・百鬼・変化（へんげ）・魔・魔物・物の怪（勿の怪）・物の気・妖異・妖怪変化なども同様な意味で使われる。