Two closely related concepts play an essential role in cross-cultural comparisons, namely equivalence and bias (Poortinga, 1989; Van de Vijver, 2015). There is no consensual definition of either concept in the cross-cultural literature. Johnson (1998) identified more than fifty types of definitions of equivalence, addressing dissimilar features, such as constructs, methodology, language, and context. All definitions refer to some aspect that is shared across cultures or to a qualitative or quantitative procedure to establish the shared features. A review of bias approaches would probably show a comparable variety.