Cannot be separated even for a moment; utterly indispensable or vitally important.
对于一个长期在野外探险的旅行者来说，地图和指南针是不可须臾离的。
For a traveler on a long wilderness expedition, a map and a compass are utterly indispensable.
Next Idiom
Cannot be separated even for a moment; utterly indispensable or vitally important.