(idiom) to be on extremely intimate terms; to have a very close relationship with no distance between one another

Working together closely with no gaps or friction; seamless collaboration; perfect collaboration characterized by perfect harmony

(Buddhism) the last and most painful of the eight hot hells, where those who committed the gravest sins suffer without interruption; also called [[阿鼻地狱|阿鼻地獄|a1 bi2 di4 yu4]]

A long road of suffering or sin, named after the [[无间地狱|無間地獄|wu2 jian4 di4 yu4]] or Avici hell, the lowest level of hell in Buddhism where suffering is eternal and continuous; the title of the 2002 film Infernal Affairs