Necessity

"Apodictic", also spelled "apodeictic" (, "capable of demonstration"), is an adjectival expression from Aristotelean logic that refers to propositions that are demonstrably, necessarily or self-evidently true. Apodicticity or apodixis is the corresponding abstract noun, referring to logical certainty.

formal way of expressing the meaning of a conditional sentence

Necessitarianism is a metaphysical principle that denies all mere possibility; there is exactly one way for the world to be.

type of fallacy in modal logic