  It is hard to give a flavor of the terminological explanations (TEs) in a short space: their complexity and cumulative effect has to appreciated at first hand. The most thorough account is in the TEs for Protothetic in Grundzüge, Section 11, and there is also a compressed account of TEs for Ontology. A somewhat more manageable set for a version of propositional calculus with definitions, based on Łukasiewicz’s bracketless notation, is given in the 1931 paper ‘Über Definitionen in der sogenannten Theorie der Deduktion’, and based on lectures from 1930–31. There Leśniewski gives TEs in words rather than symbolic abbreviations, and with copious examples. Nevertheless, it is intellectually challenging, since for all the complex TEs (metalogical definitions), Leśniewski demanded logical independence of all the various clauses, to be shown by suitable models. As a result, it took graduate students three semesters to work through a set of TEs in Leśniewski’s seminar (personal information from Czesław Lejewski) .