“…We also complement our study of negation as impossibility by introducing and studying a possibility operator, where we provide standard relational semantics, despite the lack of distribution, thus significantly improving over the results of Conradie and Palmigiano (2015), which follows the approach of Gehrke (2006) of so-called generalized Kripke frames, or of Suzuki (2010Suzuki ( , 2012Suzuki ( , 2014, as well as of Järvinen and Orlowska (2005). The systems we study are based on non-distributive lattice logic, variously extending it with negation operators (minimal negation, De Morgan or intuitionistic negation, negation as impossibility, etc.)…”