When two waves of equal amplitude, wavelength, and frequency travel in opposite directions along a string, they interfere and form a standing wave. A standing wave has fixed points called nodes where the string does not move at all, and points of maximum amplitude called antinodes. The distance between nodes and antinodes is half the wavelength, and between a node and adjacent antinode is a quarter wavelength. All points between nodes oscillate in phase. The speed is greatest at antinodes and reduces to zero at nodes. Refer to the textbook for more detailed equations and explanations of standing waves.