  There are in Leśniewski two basic categories: sentence (S) and name (N). In Protothetic, only the former is used: Ontology and Mereology add the latter. The distinction between sentences and names is ultimate: what we can say about sentences is that they are there to say things that are true or false (obviously from a logical point of view we are overlooking questions and commands), whereas names are there to denote things. Leśniewski, following tradition, allows names to denote several things, or one thing, or indeed no things as all. So ‘Istanbul’ denotes one thing, namely the Turkish city, ‘city’ denotes many things, namely all cities, and ‘unicorn’ denotes nothing at all. In Leśniewski’s mature work Mill’s notion of connotation is dropped, along with the concept of property which it employs, so the sole logical function of names is denoting. Again following tradition rather than the modern approach of Frege and Russell, Leśniewski makes no syntactic distinction between general terms or common nouns on the one hand and singular terms or proper names on the other. This is often said to be because his native Polish lacks definite and indefinite articles, which make the distinction more grammatically obvious, but this conjecture is nonsense because Leśniewski spoke and wrote fluent German, and German is awash with articles. It seems much more likely that Leśniewski deliberately chose to follow the traditional rather than the modern way because he thought it both more expressively powerful and closer to natural language.