From Latin 'sextans' (a sixth)—the instrument's 60° arc is one-sixth of a full circle.
A navigational instrument with a graduated arc of 60 degrees, used for measuring the angular distance between objects, especially for determining latitude at sea.
From Latin 'sextans' (a sixth part), from 'sextus' (sixth), because the instrument's arc is one-sixth of a full circle (60°). It replaced the earlier quadrant (quarter-circle) and octant (eighth-circle). The 'sixth' in sextant is the same as in 'semester' (six months). Key roots: sextus (Latin: "sixth"), *sweks (Proto-Indo-European: "six").