nimber
In mathematics, in combinatorial game theory, nimbers are special games, defined as Nim games at a pile with an infinitely infinite number of matches. More precisely, the nimber corresponding to the ordinal number, often denoted * is defined as the match pile of the Nim game with a number of matches. A nimber can also directly designate the number of matches. The nimbers intervene in particular in the theory of impartial games: in fact, according to the Sprague-Grundy theorem, every impartial game is equivalent to a certain nimber.