- 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.
- Amsterdam (Wikipedia)
Amsterdam (/ˈæmstərdæm/ AM-stər-dam, UK also /ˌæmstərˈdæm/ AM-stər-DAM, Dutch: [ˌɑmstərˈdɑm]; literally, “The Dam on the River Amstel”) is the capital and most populated city of the Netherlands, with The Hague being the seat of government. It has a population of 921,402 within the city proper, 1,457,018 in the urban area and 2,480,394 in the metropolitan area. Located in the Dutch province of North Holland, Amsterdam is colloquially referred to as the “Venice of the North”, for its large number of canals, now designated a UNESCO World Heritage Site.