Complex sentence: A hospital ship is a ship designated for primary function as a floating medical treatment facility or hospital; most are operated by the military forces (mostly navies) of various countries, as they are intended to be used in or near war zones.
Split into simpler sentences: A hospital ship is a ship designated for primary function as a floating medical treatment facility or hospital. Most are operated by the military forces (mostly navies) of various countries, as they are intended to be used in or near war zones.