Stratum (in neurocognitive linguistics)

A stratum or stratal system is one of several layers of structure in the linguistic information system. Each stratum consists of lines and nodes organized into nections, the fundamental modules of network structure. Each stratum has distinctive patterns of arrangement of nections. Different versions of relational network theory have recognized different numbers of such stratal systems, but these differences amount to variations on a general theme of three major systems, phonological, lexico-grammatical, and semantic-conceptual. Relations between strata are called realizational.

Each stratal system includes a tactic pattern, controlling the combinations appropriate to that system. According to one common breakdown of realizational levels, these patterns are phonotactics (the structure of syllables and phonological words), morphotactics (the structure of words and grammatical phrases), lexotactics (the structures of clauses and sentences), and semotactics (the structure of thoughts, ideas, procedures, rituals, etc.)

Before 1961, strata were called levels, but the term was found to be too ambiguous, since it was being used by linguists in many different ways. The term realizational level, however, is still a valid synonym.