= Ehrenfeucht-Fraïssé game
{c}
{title2=$G_n(\mathcal M,\mathcal N)$}
In each round the Spoiler selects an element from either structure and the Duplicator responds in the other. The paired selected elements must preserve all atomic information and equality, giving a <partial isomorphism of structures>. In the infinite game the Duplicator wins by avoiding failure at every finite stage. In a timed game the Spoiler first announces the number of rounds, allowing a different response strategy for each horizon.
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