Statistics is the accepted body of methods for summarizing or describing data and drawing conclusions from the summary measures. Everyone who has data to summarize thus needs some knowledge of statistics. The first step in gaining that knowledge is to master the professional jargon. This dictionary is geared to offer more than the usual string of isolated and independent definitions: it provides also the context, applications, and related terminology. The intended audience falls into five groups with rather different needs: (1) professional statisticians who need to recall a definition, (2) scientists in disciplines other than statistics who need to know the acceptable methods of summarizing data, (3) students of statistics who need to broaden their knowl­ edge of their subject matter and make constant reference to it, (4) managers who will be reading statistical reports written by their employees, and (5) journalists who need to interpret government or scientific reports and transmit the information to the public.