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  "body": "\n## Summary\n\nA structure for a [[signature|WDVVEYD6AT]] is a set together with a meaning for each symbol of the signature.\nEach symbol becomes a function, a relation or an element of the set.\nStructures are the objects in which first-order formulas are true or false.\nGroups, rings, ordered sets and graphs are all structures for suitable signatures.\n\n## Explanations\n\n### L1 human\n\nA signature is a list of names, such as \"$+$\", \"$0$\" and \"$\u003c$\", with the number of inputs of each name.\nA structure picks a set and says what each name means on that set.\nFor example, the integers with ordinary addition, the number zero and the usual order form a structure for the signature with $+$, $0$ and $\u003c$.\nThe same signature can have many different structures, such as the rational numbers with the same symbols.\n",
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