- Dystopia (Wikipedia)
A dystopia (from Ancient Greek δυσ (dus) ‘bad’, and τόπος (tópos) ‘place’), also called a cacotopia or anti-utopia, is a community or society that is extremely bad or frightening. It is often treated as an antonym of utopia, a term that was coined by Sir Thomas More and figures as the title of his best known work, published in 1516, which created a blueprint for an ideal society with minimal crime, violence, and poverty. The relationship between utopia and dystopia is in actuality, not one simple opposition, as many utopian elements and components are found in dystopias as well, and vice versa.
- Axiom of choice (Wikipedia)
In mathematics, the axiom of choice, abbreviated AC or AoC, is an axiom of set theory equivalent to the statement that a Cartesian product of a collection of non-empty sets is non-empty. Informally put, the axiom of choice says that given any collection of sets, each containing at least one element, it is possible to construct a new set by choosing one element from each set, even if the collection is infinite.