In justification logics, instead of the familiar \(KX\) of epistemic logic we have \(t{:}X\), where \(t\) is an explicit justification term. The formula \(t{:}X\) is read, “\(X\) is known for reason \(t\).” Justification terms have structure which varies depending on the particular justification logic being investigated. Common to all justification logics is the following minimal machinery. First there are justification constants, intended to be unanalyzed justifications of accepted logical truths. Second, there are justification variables, standing for arbitrary justifications. And finally there are binary operations, minimally \(\cdot\) and \(+\). The intention is that if \(s\) justifies \(X \supset Y\) and \(t\) justifies \(X\), then \(s\cdot t\) justifies \(Y\), and also \(s+t\) justifies anything that \(s\) justifies and also anything that \(t\) justifies. There are very close connections between justification logics and epistemic logics, embodied in Realization Theorems. This is not the appropriate place to go into details; a thorough discussion of justification logics can be found in this encyclopedia's entry on justification logic.