A solid-state system in which the spatial dimension is less than three. In practice, a two-dimensional system is a thin film or layer and a one-dimensional system is a thin wire. Two-dimensional systems have applications to semiconductor technology, in such devices as MOSFETs (see transistor). The behaviour of low-dimensional systems is of interest because the problems for low-dimensional systems (particularly one-dimensional systems) are much easier to solve than the corresponding problems in three dimensions. Clusters of atoms and very small crystals can be considered as zero-dimensional systems.