This working paper introduces the notation and basic concepts that are used throughout the OPHI Working Papers 82-91. The Paper has five sections. First we review unidimensional poverty measurement with particular attention to the well-known Foster-Greer-Thorbecke measures of income poverty as many methods presented in OPHI Working Paper 84 (Chapter 3 – Overview of Methods for Multidimensional Poverty Assessment) as well as the measure presented in OPHI Working Papers 86-90 (Chapters 5-9) are based on these measures. The second section introduces the notation and basic concepts for multidimensional poverty measurement that are used in subsequent chapters. Third we define indicators’ scales of measurement, and fourth, addressissues of comparability across people and dimensions. The fifth section systematically explains different properties that have been proposed in axiomatic approaches to multidimensional poverty measurement, which enable the analyst to understand the ethical principles embodied in a measure and to be aware of the direction of change they will exhibit under certain transformations.