This special issue focuses on the theoretical and empirical underpinnings of truth-marking. The names that have been used to refer to this phenomenon include, among others, counter-assertive focus, polar(ity) focus, verum focus, emphatic polarity or simply verum. This terminological variety is suggestive of the wide range of ideas and conceptions that characterizes this research field. This collection aims to get closer to the core of what truly constitutes verum. We want to expand the empirical base and determine the common and diverging properties of truth-marking in the languages of the world. The objective is to set a theoretical and empirical baseline for future research on verum and related phenomena.