Standing waves form by superposition of two identical waves travelling in opposite directions. Result: $y = 2A\sin(kx)\cos(\omega t)$. Properties: (1) No energy transfer — energy oscillates between KE and PE locally. (2) Amplitude varies with position: $2A|\sin(kx)|$. (3) All particles between two nodes oscillate in phase. (4) Particles on opposite sides of a node are in antiphase. (5) Nodes are permanently at rest; antinodes have maximum amplitude $2A$. Distance between consecutive nodes = $\lambda/2$; between a node and adjacent antinode = $\lambda/4$.