It will be clear from the discussion so far that Freud uses the term "unconscious' in several ways. Sometimes the term is used to designate a functional system of the mind containing mental representations that are unconscious but not preconscious. (and possessing special irrational characteristics, described below). Following Freud, I will refer to this as "System Ucs." or just Ucs." I will also refer to this sense of "unconscious' as "unconscious_irr". At other times Freud uses "unconscious' to denote all of those mental items that are not consciously represented. This includes the contents of System Ucs. as well as the contents of system Pcs. Freud refers to these items as "descriptively" unconscious. I will refer to this as "unconscious_desc" Finally, Freud sometimes describes as "unconscious' all mental items under neuroscientific descriptions ("unconscious_nen").