By treating words such as "POINT" and "LINE" as if they had only the meaning instilled in them by the propositions in which they occur, we take a step towards complete formalization of geometry. This semiformal version still uses a lot of words in Englishwith their usual meanings (words such as "the", 'if", "and", "join", "have"), although the everyday meaning has been drained out of special words like "POINT" and "LINE", which are con sequently called undefined terms. Undefined terms, like the p and q of the pq-system, do get defined in a sense: implicitly—by the totality of all proposi tions in which they occur, rather than explicitly, in a definition.