A device consisting of a magnetic needle that points north, allowing its user to determine their heading.
The world's first recorded evidence of a compass is believed to be the Dream Pool Essays written by Shen Kuo.
Military compasses supplied by the US military are marked with mil graduations and have a needle or dial that floats on oil. A mil is a unit of angular measurement. When a compass is 1 mil off target, it equates to 1 meter of separation at 1000 meters.