in geometry, a line or radius falling perpendicularly CATETUS of incidence, in catoptrics, a right line drawn from a point of the object, perpendicular to the reflecting line.

CATETUS of reflection, or of the eye, a right line drawn from the eye, perpendicular to the reflecting line.

CATETUS of obliquation, a right line drawn perpendicular to the speculum, in the point of incidence or reflection.

CATETUS, in architecture, a perpendicular line, supposed to pass through the middle of a cylindrical body, as a baluster, column, &c.