Path length can refer to:
Physics Travel path length, the total distance an object travels dependent on its path through space Optical path length, the product of the distance light travels and the refractive index of the medium it travels through Mean free path, the average distance that a particle travels before scattering Radiation length, a characteristic length for the decay of radiation in a medium
Networks and computing Average path length, the average number of steps along the shortest paths for all possible pairs of network nodes Hop count, the number of intermediate network devices through which data must pass between source and destination in a computer network Instruction path length, the number of machine code instructions required to execute a section of a computer program