the logical study of necessity and possibility
a system of logic whose formal properties resemble certain moral and epistemological concepts
A system of logic which studies how to combine propositions which include the concepts of necessity, possibility, and obligation.
Any formal system that attempts to deal with modalities, such as possibility and necessity, but also obligation and permission.
Modal logic is a type of formal logic primarily developed in the 1960s that extends classical propositional and predicate logic to include operators expressing modality. Modals—words that express modalities—qualify a statement. For example, the statement "John is happy" might be qualified by saying that John is usually happy, in which case the term "usually" is functioning as a modal. The traditional alethic modalities, or modalities of truth, include possibility, necessity, and impossibility. Other modalities that have been formalized in modal logic include temporal modalities, or modalities of time, deontic modalities, epistemic modalities, or modalities of knowledge and doxastic modalities, or modalities of belief. A formal modal logic represents modalities using modal operators. For example, "It might rain today" and "It is possible that rain will fall today" both contain the notion of possibility. In a modal logic this is represented as an operator, Possibly, attached to the sentence "It will rain today".
The numerical value of modal logic in Chaldean Numerology is: 9
The numerical value of modal logic in Pythagorean Numerology is: 1