Preface and currently work or have professional experience as an epidemiologist you may also have professional experience in other fields, "27% answered"While my main job is not as an epidemiologist, I often use epidemiologic knowledge, methods or reasoning in my work, " 2% selected"I have little to no training in epidemiology and I seldom or never use it in my work lyour contribution nevertheless welcomed, "and 4%"Other. " These data provide a factual back ground for the next paragraphs. Is this dictionary an attempt to demarcate epidemiology neatly? I dont think oOr Id rather think it is not, to the extent that a dictionary can-or needs to-avoid demarcating a discipline. 4 Yet like many other scientists, every now and then epidemiologists engage in boundary-making endeavors and disciplinary demarcation. And then, as usual in other disciplines, epidemiologists assert or reclaim contested epistemic authority and may claim jurisdiction over areas of public health, medicine, statistics, or science. These efforts evolved in the course of the twentieth century while epidemiology developed as a very diverse, eclectic- and foremost, integrative-field of practice and academic discipline. -l2 And so will they evolve as the societies of the twenty-first century continue developing There is nothing wrong with that, it is the natural thing Is this dictionary an epistemic space? Well, of course it is, in the broadest sense: a space of knowledge. Does it belong to an epistemic community or to more than one? Both answers are true. It belongs to one very diverse community of knowledge-epidemiologists around the globe. And to a lesser but no less impor tant extent, the dictionary pertains also to the many communities of knowledge that interact and cooperate with epidemiology, or with which epidemiology cooperates, or that simply use epidemiological reasoning, knowledge, methods, or techniques. No matter how many mistakes we may have made(eventually, they are all m responsibility), I would like to think that in making this new edition we again practiced a high level of scientific and intellectual rigor in two opposite and omplementary directions: (1) in selecting and defining terms that are at the ontological, epistemological, and methodological core of epidemiology, and (2)in selecting and defining terms that are near or within disciplines with which epidemiology maintains vital interactions-vital for epidemiology, the other disciplines, science, and society These I take to be facts: today research methods with strong epidemiological roots and properties are fruitfully applied"within"and"outside"epidemiology A positive blurring of the boundaries of epidemiological research methods occurred in the last decades of the last century: e. g, the integration of population thinking and group comparison into clinical and public health research. 10 The expansion of this influence toward other research areas remains a significant-and in my view highly attractive-challenge for many scientists. Such an expansion of influence will not be identical to what occurred via clinical epidemiology and, later, evidence-based medicine and, today evidence-based health care The nature of the hypotheses at stake is often quite different in clinical medicineand currently work or have professional experience as an epidemiologist [you may also have professional experience in other fi elds],” 27% answered “While my main job is not as an epidemiologist, I often use epidemiologic knowledge, methods or reasoning in my work,” 2% selected “I have little to no training in epidemiology and I seldom or never use it in my work [your contribution is nevertheless welcomed],” and 4% “Other.” These data provide a factual back￾ground for the next paragraphs. Is this dictionary an attempt to demarcate epidemiology neatly? I don’t think so. Or I’d rather think it is not, to the extent that a dictionary can—or needs to—avoid demarcating a discipline.4 Yet like many other scientists, every now and then epidemiologists engage in boundary-making endeavors and disciplinary demarcation. And then, as usual in other disciplines, epidemiologists assert or reclaim contested epistemic authority and may claim jurisdiction over areas of public health, medicine, statistics, or science. These efforts evolved in the course of the twentieth century while epidemiology developed as a very diverse, eclectic— and foremost, integrative—fi eld of practice and academic discipline.4–12 And so will they evolve as the societies of the twenty-fi rst century continue developing. There is nothing wrong with that, it is the natural thing. Is this dictionary an epistemic space? Well, of course it is, in the broadest sense: a space of knowledge. Does it belong to an epistemic community or to more than one? Both answers are true. It belongs to one very diverse community of knowledge—epidemiologists around the globe. And to a lesser but no less impor￾tant extent, the dictionary pertains also to the many communities of knowledge that interact and cooperate with epidemiology, or with which epidemiology cooperates, or that simply use epidemiological reasoning, knowledge, methods, or techniques. No matter how many mistakes we may have made (eventually, they are all my responsibility), I would like to think that in making this new edition we again practiced a high level of scientifi c and intellectual rigor in two opposite and complementary directions: (1) in selecting and defi ning terms that are at the ontological, epistemological, and methodological core of epidemiology, and (2) in selecting and defi ning terms that are near or within disciplines with which epidemiology maintains vital interactions—vital for epidemiology, the other disciplines, science, and society. These I take to be facts: today research methods with strong epidemiological roots and properties are fruitfully applied “within” and “outside” epidemiology. A positive blurring of the boundaries of epidemiological research methods occurred in the last decades of the last century; e.g., the integration of population thinking and group comparison into clinical and public health research.10 The expansion of this infl uence toward other research areas remains a signifi cant—and in my view highly attractive—challenge for many scientists. Such an expansion of infl uence will not be identical to what occurred via clinical epidemiology and, later, evidence-based medicine and, today, evidence-based health care. The nature of the hypotheses at stake is often quite different in clinical medicine xi Preface