Writing is a cognitive and social activity involving neuropsychological and physical processes and the use of writing systems to structure and translate human thoughts into persistent representations of human language. A system of writing relies on many of the same semantic structures as the language it represents, such as lexicon and syntax, with the added dependency of a system of symbols representing that language's phonology and morphology. Nevertheless, written language may take on characteristics distinctive from any available in spoken language. The outcome of this activity, also called "writing", and sometimes a "text", is a series of physically inscribed, mechanically transferred, or digitally represented linguistic symbols. The interpreter or activator of a text is called a "reader". Writing systems do not themselves constitute languages (with the debatable exception of computer languages); they are a means of rendering language into a form that can be read and reconstructed by other humans separated by time and/or space. While not all languages use a writing system, those that do can complement and extend the capacities of spoken language by creating durable forms of language that can be transmitted across space (e.g. written correspondence) and stored over time (e.g. libraries or other public records). Writing can also have knowledge-transforming effects, since it allows humans to externalize their thinking in forms that are easier to reflect on, elaborate on, reconsider, and revise. Writing implement Any instance of writing involves a complex interaction among available tools, intentions, cultural customs, cognitive routines, genres, tacit and explicit knowledge, and the constraints and limitations of the writing system(s) deployed. Inscriptions have been made with fingers, styluses, quills, ink brushes, pencils, pens, and many styles of lithography; surfaces used for these inscriptions include stone tablets, clay tablets, bamboo slats, papyrus, wax tablets, vellum, parchment, paper, copperplate, slate, porcelain, and other enameled surfaces.