Definition of principal point in English:

principal point

noun

  • 1Perspective. The point where the principal ray meets the picture plane.

  • 2Optics. Each of the two points at which the optic axis of a lens intersects the principal planes.

Origin

Late 16th century (in an earlier sense). From principal + point. In sense 1 after Middle French principal poinct.

Pronunciation

principal point

/ˌprɪnsɪpl ˈpɔɪnt/