Other forms: compasses
A compass is the instrument whose needle points to magnetic north. A ship's compass, read a compass, a compass and a map.
The needle finds magnetic north, which is not quite true north, and the difference is called declination — navigators correct for it. The compass points are north, south, east and west with their subdivisions. A pair of compasses is the different instrument for drawing circles, and in British usage the plural is standard for that one. Note moral compass, meaning somebody's sense of right and wrong, and the verb encompass, meaning to include entirely.
1nouncompassAn instrument whose needle points to north.
“The compass was the only thing that worked in the fog.”
2noundrawingAn instrument for drawing circles.
“She drew the arc with a compass and a blunt pencil.”
compass is an instrument.
Medieval Latin compassus meant a circle or a stepping around — com-, together, plus passus, a pace. The drawing instrument was named first, for the circle it makes, and the navigating one took the name from the circular card of points.
Latin
com- — together
Medieval Latin
compassus — a circle, a circuit
Old French
compas
Middle English
compas — a circle, circuit, limit, form, a mathematical instrument
English, today
compass
Built from
From Middle English compas (“a circle, circuit, limit, form, a mathematical instrument”), from Old French compas, from Medieval Latin compassus (“a circle, a circuit”), from Latin com- (“together”) + passus (“a pace, step, later a pass, way, route”); see pass, pace.
Etymology from Wiktionary, CC BY-SA