Node

A node is a point in a standing-wave pattern where the amplitude is permanently zero. The wave is oscillating around it, but the point itself never moves. For a string fixed at both ends in its nth mode, there are n + 1 nodes total: the two fixed ends, plus (n − 1) evenly spaced inside.

For a surface like a Chladni plate, nodes form curves, not points. Sand sprinkled on the plate migrates to these nodal lines and settles there, because the plate isn't moving beneath it. Physically, nodes are where two counter-propagating travelling waves always cancel exactly.