Final answer:
In a standing wave, the points that never move from their equilibrium position are called nodes, and these are the points where the wave disturbance is zero.
Step-by-step explanation:
The positions in a medium vibrating with a standing wave pattern that never move from their equilibrium positions are called nodes. These are points where the wave disturbance is zero in a standing wave. In the case of a string instrument, the fixed ends of the strings are also nodes because the string cannot move at these endpoints. The pattern of a standing wave is characterized by nodes and antinodes, which are the locations of maximum amplitude.
Typically, standing waves are formed by the superposition of two or more waves travelling in opposite directions. This phenomenon can be observed in musical instruments and is essential for the study of the electronic structure of atoms and molecules.