A curve of degree n related to a given curve C of degree n + 1 and a point P by containing every point of C whose tangent passes through P.
Usually called simply a polar. The first polar of a circle is a straight line: compare "polar". In mathematical terms: (of a point (a₀, a₁,…an) with respect to a curve described by the homogeneous function f(x₀, x₁,…xₙ) = 0) the curve represented by the equation Σᵢaᵢ ∂f/∂xᵢ = 0.
Mid 19th century; earliest use found in Augustus De Morgan (1806–1871), mathematician and historian.