In this glossary, the authors address eight key questions pertinent to health inequalities: (1) What is the distinction between health inequality and health inequity?; (2) Should we assess health inequalities themselves, or social group inequalities in health?; (3) Do health inequalities mainly reflect the effects of poverty, or are they generated by the socioeconomic gradient?; (4) Are health inequalities mediated by material deprivation or by psychosocial mechanisms?; (5) Is there an effect of relative income on health, separate from the effects of absolute income?; (6) Do health inequalities between places simply reflect health inequalities between social groups or, more significantly, do they suggest a contextual effect of place?; (7) What is the contribution of the lifecourse to health inequalities?; (8) What kinds of inequality should we study?