Referring to a node.

1. In optics, either of two points located on the axis of an optical system in such a way that a ray directed through one point emerges from the lens as if through the other point and in a parallel direction; if the same medium is on both sides of the lens, the nodal points coincide with the principal points.
2. In electricity, in a transmission system, the junction points by which automatic switches and switching centers are nodal points in automated systems.
3. In oceanography, points of zero displacement of water in amphidromic tidal systems, reduced from a line to a point by the Coriolis effect (observed deflection of something).

Also called, amphidromic points (points of almost zero tidal fluctuation on the ocean surface, represented on a chart of cotidal lines by a point from which these lines radiate).

A heart rhythm produced when a pacemaker has been inserted in the atrioventricular node.

1. Tissue from a lymph node.
2. Tissue from the sinoatrial node or atrioventricular node in the heart.

The zone in which there is no tidal rise or fall in a system of standing waves, the direction of littoral (coastal or shore region) transport differing on either side of the zone.