alethic (??li???k) adj (Logic) logic a. of or relating to such philosophical concepts as truth, necessity, possibility, contingency, etcb. designating the branch of modal logic that deals with the formalization of these concepts[C20: from Greek al?theia truth]Collins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014