axiom of determinacy

The axiom of determinacy (abbreviated as AD) is an axiom in the language of set theory (that is, one that makes an assertion about sets). It was introduced by Polish mathematicians Mycielski and Steinhaus. It states the following: Consider infinite two-person games with perfect information. Then, every game of length ω where both players choose integers is determined, i.e., one of the two players has a winning strategy.
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