The label systemic is related to the system networks used in the description of human languages. System networks capture the dimension of choice at each stratum of the linguistic system to which they are applied. The system networks of the lexicogrammar make up systemic functional grammar . A system network is a theoretical tool to describe the sets of options available in a language variety; it represents abstract choice and does not correspond to a notion of actual choice or make psychological claims. Formally system networks correspond to type lattices in formal lattice theory, although they are occasionally erroneously mistaken for flowcharts or directed decision trees. Such directionality is always only a property of particular implementations of the general notion and may be made for performance reasons in, for example, computational modelling. System networks commonly employ multiple inheritance and "simultaneous" systems, or choices, which therefore combine to generate very large descriptive spaces.