Vector which is perpendicular to said surface or manifold. In a inner product space, the inner product of the normal vector with all vectors which comprise the surface is 0.
... der Schleiermacherschen Glaubenslehre (1836)
Psychologie oder Wissenschaft vom subjektiven Geist (1837; 3rd ed., 1863)
Kritische Erläuterungen des Hegelschen ...