SYNTAX: a hierarchy of grammatical categories (the syntactic functional hierarchy) in which the verb and its arguments are nested in tense and aspect phrases, which are themselves nested in clause- and discourse-marking phrases (Chomsky, 1995)

SEMANTICS a hierarchy of categories of linguistic meaning from event (kind), to event situated in a time and world (token), to situations related to speakers and anchored to a discourse (Ramchand & Svenonius, 2014)

BRAIN: a hierarchy of embedded, interconnected networks of functional connectivity that extend from segregated regions dependent on external stimuli toward integrated regions independent of external stimuli (the Sensorimotor to Association axis), and these regions' associated functions (the neural functional hierarchy): sensation and perception, working memory and attention, and social cognition, narrative, and internal mentation (Margulies et al., 2023)

CONCEPTS: a hierarchy of conceptual categories increasingly abstracted away from sensorimotor representations, to those linking representations of the external to representations of the internal, to entirely internal thoughts independent of sensorimotor representations (Wing & Tabor, in prep)