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Elementary equivalence

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gives a countable elementary substructure for any infinite first-order structure in at most countable signature; the upward Löwenheim–Skolem theorem gives elementary extensions of any infinite first-order structure of arbitrarily large cardinality.
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More generally, any first-order theory with an infinite model has non-isomorphic, elementarily equivalent models, which can be obtained via the
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to be an elementary substructure. It can be useful for constructing an elementary substructure of a large structure.
694:{\displaystyle N\models \varphi (a_{1},\dots ,a_{n}){\text{ if and only if }}M\models \varphi (a_{1},\dots ,a_{n}).} 2825: 2415: 1809: 1777: 1468: 1352: 148: 1542: 447: 3115: 3064: 2961: 2459: 2420: 1897: 48: 2956: 1571: 2886: 2425: 2277: 2260: 1983: 1463: 58: 52: 44: 2788: 2765: 2726: 2612: 2553: 2199: 2119: 1963: 1907: 1520: 3078: 2783: 2750: 2643: 2489: 2474: 2447: 2398: 2282: 2217: 2042: 2008: 2003: 1877: 1708: 1685: 69: 438:
with its usual order are elementarily equivalent, since they both interpret '<' as an unbounded dense
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For example, consider the language with one binary relation symbol '<'. The model
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is complete if and only if any two of its models are elementarily equivalent.
442:. This is sufficient to ensure elementary equivalence, because the theory of 3120: 3023: 2076: 1993: 1953: 1917: 1853: 1665: 1655: 1628: 240: 3105: 2903: 2351: 2056: 1650: 372:
if every first-order sentence (formula without free variables) over 
333:. One can prove that two structures are elementarily equivalent with the 703:
This definition first appears in Tarski, Vaught (1957). It follows that
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Elementary embeddings are the most important maps in model theory. In
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together with a new constant symbol for every element of 
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The use of elementary substructures in combinatorics
3047: 2942: 2774: 2667: 2519: 2212: 2135: 2029: 1933: 1822: 1749: 1684: 1599: 1590: 1512: 1429: 1371: 1223: 1181: 1054: 996: 977: 844: 806: 730:can be interpreted as structures in the signature 693: 469:Elementary substructures and elementary extensions 57:but its sources remain unclear because it lacks 1266:, and its image is an elementary substructure. 340:Elementary embeddings are used in the study of 1407: 914:if and only if for every first-order formula 8: 1309:, vol. 136, issues 1--3, 1994, pp.243--252. 289:is elementary if and only if it passes the 2233: 1828: 1596: 1414: 1400: 1392: 1216: 1174: 1047: 989: 970: 837: 799: 679: 660: 639: 630: 611: 593: 88:Learn how and when to remove this message 1273:, elementary embeddings whose domain is 404:are elementarily equivalent, one writes 274:) is an elementary substructure of  1294: 7: 446:is complete, as can be shown by the 430:with its usual order and the model 991: 352:Elementarily equivalent structures 215:if and only if it is true in  25: 910:is an elementary substructure of 787:is an elementary substructure of 751:is an elementary substructure of 223:is an elementary substructure of 3133: 1262:Every elementary embedding is a 1121:such that for every first-order 444:unbounded dense linear orderings 34: 771:are elementarily equivalent as 457:. Thus, for example, there are 685: 653: 636: 604: 504:such that for all first-order 1: 3094:History of mathematical logic 380:if and only if it is true in 3019:Primitive recursive function 1031:), then there is an element 894:be a structure of signature 325:also has a solution in  293:: every first-order formula 584:if and only if it holds in 496:are structures of the same 364:of the same signature  3186: 2083:Schröder–Bernstein theorem 1810:Monadic predicate calculus 1469:Foundations of mathematics 1353:Cambridge University Press 641: if and only if  3160:Equivalence (mathematics) 3129: 3116:Philosophy of mathematics 3065:Automated theorem proving 2236: 2190:Von Neumann–Bernays–Gödel 1831: 335:Ehrenfeucht–FraĂŻssĂ© games 130:if they satisfy the same 1370:Monk, J. Donald (1976), 1224:{\displaystyle \models } 1182:{\displaystyle \models } 1055:{\displaystyle \models } 997:{\displaystyle \exists } 978:{\displaystyle \models } 860:Löwenheim–Skolem theorem 845:{\displaystyle \succeq } 807:{\displaystyle \preceq } 455:Löwenheim–Skolem theorem 43:This article includes a 2766:Self-verifying theories 2587:Tarski's axiomatization 1538:Tarski's undefinability 1533:incompleteness theorems 877:Tarski–Vaught criterion 478:elementary substructure 396:first-order theory. If 370:elementarily equivalent 329:when evaluated in  321:that has a solution in 161:elementary substructure 128:elementarily equivalent 72:more precise citations. 27:Concept in model theory 18:Elementarily equivalent 3140:Mathematics portal 2751:Proof of impossibility 2399:propositional variable 1709:Propositional calculus 1349:A shorter model theory 1225: 1183: 1105:of the same signature 1056: 998: 979: 846: 808: 695: 528:) with free variables 3009:Kolmogorov complexity 2962:Computably enumerable 2862:Model complete theory 2654:Principia Mathematica 1714:Propositional formula 1543:Banach–Tarski paradox 1305:(1993). Appearing in 1226: 1184: 1089:Elementary embeddings 1057: 999: 980: 847: 809: 759:is a substructure of 718:is a substructure of 707:is a substructure of 696: 317:) with parameters in 167:if every first-order 2957:Church–Turing thesis 2944:Computability theory 2153:continuum hypothesis 1671:Square of opposition 1529:Gödel's completeness 1307:Discrete Mathematics 1215: 1173: 1095:elementary embedding 1046: 988: 969: 836: 823:elementary extension 798: 592: 256:elementary embedding 233:elementary extension 3111:Mathematical object 3002:P versus NP problem 2967:Computable function 2761:Reverse mathematics 2687:Logical consequence 2564:primitive recursive 2559:elementary function 2332:Free/bound variable 2185:Tarski–Grothendieck 1704:Logical connectives 1634:Logical equivalence 1484:Logical consequence 1264:strong homomorphism 1145:) and all elements 544:, and all elements 482:elementary submodel 459:non-standard models 3165:Mathematical logic 2909:Transfer principle 2872:Semantics of logic 2857:Categorical theory 2833:Non-standard model 2347:Logical connective 1474:Information theory 1423:Mathematical logic 1374:Mathematical Logic 1323:Keisler, H. Jerome 1221: 1179: 1052: 994: 975: 902:a substructure of 873:Tarski–Vaught test 867:Tarski–Vaught test 842: 804: 691: 291:Tarski–Vaught test 191:) with parameters 106:mathematical logic 45:list of references 3147: 3146: 3079:Abstract category 2882:Theories of truth 2692:Rule of inference 2682:Natural deduction 2663: 2662: 2208: 2207: 1913:Cartesian product 1818: 1817: 1724:Many-valued logic 1699:Boolean functions 1582:Russell's paradox 1557:diagonal argument 1454:First-order logic 1362:978-0-521-58713-6 1336:978-0-444-88054-3 1319:Chang, Chen Chung 1208:) if and only if 1101:into a structure 942:and all elements 642: 98: 97: 90: 16:(Redirected from 3177: 3138: 3137: 3089:History of logic 3084:Category of sets 2977:Decision problem 2756:Ordinal analysis 2697:Sequent calculus 2595:Boolean algebras 2535: 2534: 2509: 2480:logical/constant 2234: 2220: 2143:Zermelo–Fraenkel 1894:Set operations: 1829: 1766: 1597: 1577:Löwenheim–Skolem 1464:Formal semantics 1416: 1409: 1402: 1393: 1388: 1377: 1365: 1339: 1310: 1299: 1245:), â€Š,  1230: 1228: 1227: 1222: 1188: 1186: 1185: 1180: 1061: 1059: 1058: 1053: 1003: 1001: 1000: 995: 984: 982: 981: 976: 851: 849: 848: 843: 813: 811: 810: 805: 700: 698: 697: 692: 684: 683: 665: 664: 643: 640: 635: 634: 616: 615: 463:Peano arithmetic 436:rational numbers 93: 86: 82: 79: 73: 68:this article by 59:inline citations 38: 37: 30: 21: 3185: 3184: 3180: 3179: 3178: 3176: 3175: 3174: 3150: 3149: 3148: 3143: 3132: 3125: 3070:Category theory 3060:Algebraic logic 3043: 3014:Lambda calculus 2952:Church encoding 2938: 2914:Truth predicate 2770: 2736:Complete theory 2659: 2528: 2524: 2520: 2515: 2507: 2227: and  2223: 2218: 2204: 2180:New Foundations 2148:axiom of choice 2131: 2093:Gödel numbering 2033: and  2025: 1929: 1814: 1764: 1745: 1694:Boolean algebra 1680: 1644:Equiconsistency 1609:Classical logic 1586: 1567:Halting problem 1555: and  1531: and  1519: and  1518: 1513:Theorems ( 1508: 1425: 1420: 1386: 1369: 1363: 1345:Hodges, Wilfrid 1343: 1337: 1317: 1314: 1313: 1300: 1296: 1291: 1279:large cardinals 1257: 1244: 1213: 1212: 1207: 1199:, â€Š,  1198: 1171: 1170: 1158: 1152:, â€Š,  1151: 1144: 1136:, â€Š,  1135: 1097:of a structure 1091: 1084: 1076:, â€Š,  1075: 1044: 1043: 1030: 1022:, â€Š,  1021: 986: 985: 967: 966: 957: 949:, â€Š,  948: 937: 929:, â€Š,  928: 883:of a structure 869: 834: 833: 796: 795: 779: 755:if and only if 738: 675: 656: 626: 607: 590: 589: 579: 573:, â€Š,  572: 557: 551:, â€Š,  550: 543: 535:, â€Š,  534: 527: 519:, â€Š,  518: 471: 448:Ɓoƛ–Vaught test 440:linear ordering 356:Two structures 354: 342:large cardinals 316: 308:, â€Š,  307: 281:A substructure 206: 198:, â€Š,  197: 190: 182:, â€Š,  181: 94: 83: 77: 74: 63: 49:related reading 39: 35: 28: 23: 22: 15: 12: 11: 5: 3183: 3181: 3173: 3172: 3167: 3162: 3152: 3151: 3145: 3144: 3130: 3127: 3126: 3124: 3123: 3118: 3113: 3108: 3103: 3102: 3101: 3091: 3086: 3081: 3072: 3067: 3062: 3057: 3055:Abstract logic 3051: 3049: 3045: 3044: 3042: 3041: 3036: 3034:Turing machine 3031: 3026: 3021: 3016: 3011: 3006: 3005: 3004: 2999: 2994: 2989: 2984: 2974: 2972:Computable set 2969: 2964: 2959: 2954: 2948: 2946: 2940: 2939: 2937: 2936: 2931: 2926: 2921: 2916: 2911: 2906: 2901: 2900: 2899: 2894: 2889: 2879: 2874: 2869: 2867:Satisfiability 2864: 2859: 2854: 2853: 2852: 2842: 2841: 2840: 2830: 2829: 2828: 2823: 2818: 2813: 2808: 2798: 2797: 2796: 2791: 2784:Interpretation 2780: 2778: 2772: 2771: 2769: 2768: 2763: 2758: 2753: 2748: 2738: 2733: 2732: 2731: 2730: 2729: 2719: 2714: 2704: 2699: 2694: 2689: 2684: 2679: 2673: 2671: 2665: 2664: 2661: 2660: 2658: 2657: 2649: 2648: 2647: 2646: 2641: 2640: 2639: 2634: 2629: 2609: 2608: 2607: 2605:minimal axioms 2602: 2591: 2590: 2589: 2578: 2577: 2576: 2571: 2566: 2561: 2556: 2551: 2538: 2536: 2517: 2516: 2514: 2513: 2512: 2511: 2499: 2494: 2493: 2492: 2487: 2482: 2477: 2467: 2462: 2457: 2452: 2451: 2450: 2445: 2435: 2434: 2433: 2428: 2423: 2418: 2408: 2403: 2402: 2401: 2396: 2391: 2381: 2380: 2379: 2374: 2369: 2364: 2359: 2354: 2344: 2339: 2334: 2329: 2328: 2327: 2322: 2317: 2312: 2302: 2297: 2295:Formation rule 2292: 2287: 2286: 2285: 2280: 2270: 2269: 2268: 2258: 2253: 2248: 2243: 2237: 2231: 2214:Formal systems 2210: 2209: 2206: 2205: 2203: 2202: 2197: 2192: 2187: 2182: 2177: 2172: 2167: 2162: 2157: 2156: 2155: 2150: 2139: 2137: 2133: 2132: 2130: 2129: 2128: 2127: 2117: 2112: 2111: 2110: 2103:Large cardinal 2100: 2095: 2090: 2085: 2080: 2066: 2065: 2064: 2059: 2054: 2039: 2037: 2027: 2026: 2024: 2023: 2022: 2021: 2016: 2011: 2001: 1996: 1991: 1986: 1981: 1976: 1971: 1966: 1961: 1956: 1951: 1946: 1940: 1938: 1931: 1930: 1928: 1927: 1926: 1925: 1920: 1915: 1910: 1905: 1900: 1892: 1891: 1890: 1885: 1875: 1870: 1868:Extensionality 1865: 1863:Ordinal number 1860: 1850: 1845: 1844: 1843: 1832: 1826: 1820: 1819: 1816: 1815: 1813: 1812: 1807: 1802: 1797: 1792: 1787: 1782: 1781: 1780: 1770: 1769: 1768: 1755: 1753: 1747: 1746: 1744: 1743: 1742: 1741: 1736: 1731: 1721: 1716: 1711: 1706: 1701: 1696: 1690: 1688: 1682: 1681: 1679: 1678: 1673: 1668: 1663: 1658: 1653: 1648: 1647: 1646: 1636: 1631: 1626: 1621: 1616: 1611: 1605: 1603: 1594: 1588: 1587: 1585: 1584: 1579: 1574: 1569: 1564: 1559: 1547:Cantor's  1545: 1540: 1535: 1525: 1523: 1510: 1509: 1507: 1506: 1501: 1496: 1491: 1486: 1481: 1476: 1471: 1466: 1461: 1456: 1451: 1446: 1445: 1444: 1433: 1431: 1427: 1426: 1421: 1419: 1418: 1411: 1404: 1396: 1390: 1389: 1384: 1367: 1361: 1341: 1335: 1312: 1311: 1301:E. C. Milner, 1293: 1292: 1290: 1287: 1283:Critical point 1260: 1259: 1253: 1242: 1220: 1203: 1196: 1178: 1156: 1149: 1140: 1133: 1090: 1087: 1080: 1073: 1051: 1026: 1019: 993: 974: 953: 946: 933: 926: 868: 865: 841: 817:and says that 803: 775: 739:consisting of 734: 690: 687: 682: 678: 674: 671: 668: 663: 659: 655: 652: 649: 646: 638: 633: 629: 625: 622: 619: 614: 610: 606: 603: 600: 597: 577: 570: 555: 548: 539: 532: 523: 516: 470: 467: 415:A first-order 392:have the same 353: 350: 346:rank-into-rank 312: 305: 202: 195: 186: 179: 104:, a branch of 96: 95: 53:external links 42: 40: 33: 26: 24: 14: 13: 10: 9: 6: 4: 3: 2: 3182: 3171: 3168: 3166: 3163: 3161: 3158: 3157: 3155: 3142: 3141: 3136: 3128: 3122: 3119: 3117: 3114: 3112: 3109: 3107: 3104: 3100: 3097: 3096: 3095: 3092: 3090: 3087: 3085: 3082: 3080: 3076: 3073: 3071: 3068: 3066: 3063: 3061: 3058: 3056: 3053: 3052: 3050: 3046: 3040: 3037: 3035: 3032: 3030: 3029:Recursive set 3027: 3025: 3022: 3020: 3017: 3015: 3012: 3010: 3007: 3003: 3000: 2998: 2995: 2993: 2990: 2988: 2985: 2983: 2980: 2979: 2978: 2975: 2973: 2970: 2968: 2965: 2963: 2960: 2958: 2955: 2953: 2950: 2949: 2947: 2945: 2941: 2935: 2932: 2930: 2927: 2925: 2922: 2920: 2917: 2915: 2912: 2910: 2907: 2905: 2902: 2898: 2895: 2893: 2890: 2888: 2885: 2884: 2883: 2880: 2878: 2875: 2873: 2870: 2868: 2865: 2863: 2860: 2858: 2855: 2851: 2848: 2847: 2846: 2843: 2839: 2838:of arithmetic 2836: 2835: 2834: 2831: 2827: 2824: 2822: 2819: 2817: 2814: 2812: 2809: 2807: 2804: 2803: 2802: 2799: 2795: 2792: 2790: 2787: 2786: 2785: 2782: 2781: 2779: 2777: 2773: 2767: 2764: 2762: 2759: 2757: 2754: 2752: 2749: 2746: 2745:from ZFC 2742: 2739: 2737: 2734: 2728: 2725: 2724: 2723: 2720: 2718: 2715: 2713: 2710: 2709: 2708: 2705: 2703: 2700: 2698: 2695: 2693: 2690: 2688: 2685: 2683: 2680: 2678: 2675: 2674: 2672: 2670: 2666: 2656: 2655: 2651: 2650: 2645: 2644:non-Euclidean 2642: 2638: 2635: 2633: 2630: 2628: 2627: 2623: 2622: 2620: 2617: 2616: 2614: 2610: 2606: 2603: 2601: 2598: 2597: 2596: 2592: 2588: 2585: 2584: 2583: 2579: 2575: 2572: 2570: 2567: 2565: 2562: 2560: 2557: 2555: 2552: 2550: 2547: 2546: 2544: 2540: 2539: 2537: 2532: 2526: 2521:Example  2518: 2510: 2505: 2504: 2503: 2500: 2498: 2495: 2491: 2488: 2486: 2483: 2481: 2478: 2476: 2473: 2472: 2471: 2468: 2466: 2463: 2461: 2458: 2456: 2453: 2449: 2446: 2444: 2441: 2440: 2439: 2436: 2432: 2429: 2427: 2424: 2422: 2419: 2417: 2414: 2413: 2412: 2409: 2407: 2404: 2400: 2397: 2395: 2392: 2390: 2387: 2386: 2385: 2382: 2378: 2375: 2373: 2370: 2368: 2365: 2363: 2360: 2358: 2355: 2353: 2350: 2349: 2348: 2345: 2343: 2340: 2338: 2335: 2333: 2330: 2326: 2323: 2321: 2318: 2316: 2313: 2311: 2308: 2307: 2306: 2303: 2301: 2298: 2296: 2293: 2291: 2288: 2284: 2281: 2279: 2278:by definition 2276: 2275: 2274: 2271: 2267: 2264: 2263: 2262: 2259: 2257: 2254: 2252: 2249: 2247: 2244: 2242: 2239: 2238: 2235: 2232: 2230: 2226: 2221: 2215: 2211: 2201: 2198: 2196: 2193: 2191: 2188: 2186: 2183: 2181: 2178: 2176: 2173: 2171: 2168: 2166: 2165:Kripke–Platek 2163: 2161: 2158: 2154: 2151: 2149: 2146: 2145: 2144: 2141: 2140: 2138: 2134: 2126: 2123: 2122: 2121: 2118: 2116: 2113: 2109: 2106: 2105: 2104: 2101: 2099: 2096: 2094: 2091: 2089: 2086: 2084: 2081: 2078: 2074: 2070: 2067: 2063: 2060: 2058: 2055: 2053: 2050: 2049: 2048: 2044: 2041: 2040: 2038: 2036: 2032: 2028: 2020: 2017: 2015: 2012: 2010: 2009:constructible 2007: 2006: 2005: 2002: 2000: 1997: 1995: 1992: 1990: 1987: 1985: 1982: 1980: 1977: 1975: 1972: 1970: 1967: 1965: 1962: 1960: 1957: 1955: 1952: 1950: 1947: 1945: 1942: 1941: 1939: 1937: 1932: 1924: 1921: 1919: 1916: 1914: 1911: 1909: 1906: 1904: 1901: 1899: 1896: 1895: 1893: 1889: 1886: 1884: 1881: 1880: 1879: 1876: 1874: 1871: 1869: 1866: 1864: 1861: 1859: 1855: 1851: 1849: 1846: 1842: 1839: 1838: 1837: 1834: 1833: 1830: 1827: 1825: 1821: 1811: 1808: 1806: 1803: 1801: 1798: 1796: 1793: 1791: 1788: 1786: 1783: 1779: 1776: 1775: 1774: 1771: 1767: 1762: 1761: 1760: 1757: 1756: 1754: 1752: 1748: 1740: 1737: 1735: 1732: 1730: 1727: 1726: 1725: 1722: 1720: 1717: 1715: 1712: 1710: 1707: 1705: 1702: 1700: 1697: 1695: 1692: 1691: 1689: 1687: 1686:Propositional 1683: 1677: 1674: 1672: 1669: 1667: 1664: 1662: 1659: 1657: 1654: 1652: 1649: 1645: 1642: 1641: 1640: 1637: 1635: 1632: 1630: 1627: 1625: 1622: 1620: 1617: 1615: 1614:Logical truth 1612: 1610: 1607: 1606: 1604: 1602: 1598: 1595: 1593: 1589: 1583: 1580: 1578: 1575: 1573: 1570: 1568: 1565: 1563: 1560: 1558: 1554: 1550: 1546: 1544: 1541: 1539: 1536: 1534: 1530: 1527: 1526: 1524: 1522: 1516: 1511: 1505: 1502: 1500: 1497: 1495: 1492: 1490: 1487: 1485: 1482: 1480: 1477: 1475: 1472: 1470: 1467: 1465: 1462: 1460: 1457: 1455: 1452: 1450: 1447: 1443: 1440: 1439: 1438: 1435: 1434: 1432: 1428: 1424: 1417: 1412: 1410: 1405: 1403: 1398: 1397: 1394: 1387: 1385:0-387-90170-1 1381: 1376: 1375: 1368: 1364: 1358: 1354: 1351:, Cambridge: 1350: 1346: 1342: 1338: 1332: 1328: 1324: 1320: 1316: 1315: 1308: 1304: 1298: 1295: 1288: 1286: 1284: 1280: 1276: 1272: 1267: 1265: 1256: 1252: 1248: 1241: 1237: 1233: 1218: 1211: 1206: 1202: 1195: 1191: 1176: 1169: 1166: 1165: 1164: 1162: 1155: 1148: 1143: 1139: 1132: 1128: 1124: 1120: 1117: â†’  1116: 1112: 1108: 1104: 1100: 1096: 1088: 1086: 1083: 1079: 1072: 1068: 1064: 1049: 1042: 1038: 1034: 1029: 1025: 1018: 1014: 1010: 1006: 972: 965: 961: 956: 952: 945: 941: 936: 932: 925: 921: 917: 913: 909: 905: 901: 897: 893: 888: 886: 882: 878: 874: 866: 864: 861: 858:The downward 856: 854: 839: 832: 828: 824: 820: 816: 801: 794: 791:, one writes 790: 786: 781: 780:-structures. 778: 774: 770: 766: 762: 758: 754: 750: 746: 742: 737: 733: 729: 725: 721: 717: 712: 710: 706: 701: 688: 680: 676: 672: 669: 666: 661: 657: 650: 647: 644: 631: 627: 623: 620: 617: 612: 608: 601: 598: 595: 587: 583: 576: 569: 565: 561: 554: 547: 542: 538: 531: 526: 522: 515: 511: 507: 503: 499: 495: 491: 487: 483: 479: 475: 468: 466: 464: 460: 456: 451: 449: 445: 441: 437: 433: 429: 425: 420: 418: 413: 411: 408: â‰Ą  407: 403: 399: 395: 391: 387: 383: 379: 375: 371: 367: 363: 359: 351: 349: 347: 343: 338: 336: 332: 328: 324: 320: 315: 311: 304: 300: 296: 292: 288: 284: 279: 277: 273: 269: 265: 261: 257: 254:is called an 253: 250: â†’  249: 245: 242: 238: 234: 231:is called an 230: 226: 222: 218: 214: 210: 205: 201: 194: 189: 185: 178: 174: 170: 166: 162: 159:is called an 158: 154: 150: 146: 141: 139: 137: 133: 129: 125: 122: 118: 114: 111: 107: 103: 92: 89: 81: 78:February 2023 71: 67: 61: 60: 54: 50: 46: 41: 32: 31: 19: 3170:Model theory 3131: 2929:Ultraproduct 2805: 2776:Model theory 2741:Independence 2677:Formal proof 2669:Proof theory 2652: 2625: 2582:real numbers 2554:second-order 2465:Substitution 2342:Metalanguage 2283:conservative 2256:Axiom schema 2200:Constructive 2170:Morse–Kelley 2136:Set theories 2115:Aleph number 2108:inaccessible 2014:Grothendieck 1898:intersection 1785:Higher-order 1773:Second-order 1719:Truth tables 1676:Venn diagram 1459:Formal proof 1373: 1348: 1327:Model Theory 1326: 1306: 1297: 1274: 1268: 1261: 1254: 1250: 1246: 1239: 1235: 1231: 1209: 1204: 1200: 1193: 1189: 1167: 1160: 1153: 1146: 1141: 1137: 1130: 1126: 1122: 1118: 1114: 1110: 1106: 1102: 1098: 1094: 1092: 1081: 1077: 1070: 1066: 1062: 1040: 1036: 1032: 1027: 1023: 1016: 1012: 1008: 1004: 963: 959: 954: 950: 943: 939: 934: 930: 923: 919: 915: 911: 907: 903: 899: 895: 891: 889: 884: 880: 876: 872: 870: 857: 852: 830: 826: 822: 818: 814: 792: 788: 784: 782: 776: 772: 768: 764: 760: 756: 752: 748: 744: 740: 735: 731: 727: 723: 722:, then both 719: 715: 713: 708: 704: 702: 585: 581: 574: 567: 563: 559: 552: 545: 540: 536: 529: 524: 520: 513: 509: 505: 501: 493: 489: 485: 481: 477: 473: 472: 452: 431: 428:real numbers 423: 421: 414: 409: 405: 401: 397: 389: 385: 381: 377: 373: 369: 365: 361: 357: 355: 344:, including 339: 330: 326: 322: 318: 313: 309: 302: 298: 294: 290: 286: 282: 280: 275: 271: 267: 263: 259: 255: 251: 247: 243: 236: 232: 228: 224: 220: 216: 212: 208: 203: 199: 192: 187: 183: 176: 172: 168: 164: 160: 156: 152: 149:substructure 144: 142: 135: 127: 123: 119:of the same 116: 112: 102:model theory 99: 84: 75: 64:Please help 56: 3039:Type theory 2987:undecidable 2919:Truth value 2806:equivalence 2485:non-logical 2098:Enumeration 2088:Isomorphism 2035:cardinality 2019:Von Neumann 1984:Ultrafilter 1949:Uncountable 1883:equivalence 1800:Quantifiers 1790:Fixed-point 1759:First-order 1639:Consistency 1624:Proposition 1601:Traditional 1572:Lindström's 1562:Compactness 1504:Type theory 1449:Cardinality 580:) holds in 376:is true in 211:is true in 132:first-order 126:are called 70:introducing 3154:Categories 2850:elementary 2543:arithmetic 2411:Quantifier 2389:functional 2261:Expression 1979:Transitive 1923:identities 1908:complement 1841:hereditary 1824:Set theory 1289:References 1281:(see also 1271:set theory 1039:such that 508:-formulas 384:, i.e. if 138:-sentences 110:structures 3121:Supertask 3024:Recursion 2982:decidable 2816:saturated 2794:of models 2717:deductive 2712:axiomatic 2632:Hilbert's 2619:Euclidean 2600:canonical 2523:axiomatic 2455:Signature 2384:Predicate 2273:Extension 2195:Ackermann 2120:Operation 1999:Universal 1989:Recursive 1964:Singleton 1959:Inhabited 1944:Countable 1934:Types of 1918:power set 1888:partition 1805:Predicate 1751:Predicate 1666:Syllogism 1656:Soundness 1629:Inference 1619:Tautology 1521:paradoxes 1325:(1990) , 1219:⊨ 1177:⊨ 1125:-formula 1109:is a map 1050:⊨ 992:∃ 973:⊨ 840:⪰ 802:⪯ 670:… 651:φ 648:⊨ 621:… 602:φ 599:⊨ 498:signature 241:embedding 171:-formula 121:signature 3106:Logicism 3099:timeline 3075:Concrete 2934:Validity 2904:T-schema 2897:Kripke's 2892:Tarski's 2887:semantic 2877:Strength 2826:submodel 2821:spectrum 2789:function 2637:Tarski's 2626:Elements 2613:geometry 2569:Robinson 2490:variable 2475:function 2448:spectrum 2438:Sentence 2394:variable 2337:Language 2290:Relation 2251:Automata 2241:Alphabet 2225:language 2079:-jection 2057:codomain 2043:Function 2004:Universe 1974:Infinite 1878:Relation 1661:Validity 1651:Argument 1549:theorem, 1347:(1997), 1159:of  558:of  394:complete 235:of  3048:Related 2845:Diagram 2743: ( 2722:Hilbert 2707:Systems 2702:Theorem 2580:of the 2525:systems 2305:Formula 2300:Grammar 2216: ( 2160:General 1873:Forcing 1858:Element 1778:Monadic 1553:paradox 1494:Theorem 1430:General 1113::  1069:,  1015:,  938:) over 922:,  906:. Then 747:. Then 301:,  246::  227:, then 66:improve 2811:finite 2574:Skolem 2527:  2502:Theory 2470:Symbol 2460:String 2443:atomic 2320:ground 2315:closed 2310:atomic 2266:ground 2229:syntax 2125:binary 2052:domain 1969:Finite 1734:finite 1592:Logics 1551:  1499:Theory 1382:  1359:  1333:  1007:  821:is an 500:  476:is an 417:theory 108:, two 2801:Model 2549:Peano 2406:Proof 2246:Arity 2175:Naive 2062:image 1994:Fuzzy 1954:Empty 1903:union 1848:Class 1489:Model 1479:Lemma 1437:Axiom 962:, if 958:from 262:into 239:. An 219:. If 207:from 147:is a 51:, or 2924:Type 2727:list 2531:list 2508:list 2497:Term 2431:rank 2325:open 2219:list 2031:Maps 1936:sets 1795:Free 1765:list 1515:list 1442:list 1380:ISBN 1357:ISBN 1331:ISBN 898:and 890:Let 875:(or 871:The 767:and 763:and 726:and 492:and 400:and 388:and 368:are 360:and 115:and 2611:of 2593:of 2541:of 2073:Sur 2047:Map 1854:Ur- 1836:Set 1285:). 1258:)). 1163:, 1093:An 1085:). 1035:in 825:of 783:If 714:If 488:if 484:of 480:or 461:of 434:of 426:of 285:of 266:if 258:of 163:of 151:of 143:If 100:In 3156:: 2997:NP 2621:: 2615:: 2545:: 2222:), 2077:Bi 2069:In 1355:, 1321:; 855:. 829:: 711:. 588:: 562:, 450:. 412:. 348:. 337:. 278:. 140:. 55:, 47:, 3077:/ 2992:P 2747:) 2533:) 2529:( 2426:∀ 2421:! 2416:∃ 2377:= 2372:↔ 2367:→ 2362:∧ 2357:√ 2352:ÂŹ 2075:/ 2071:/ 2045:/ 1856:) 1852:( 1739:∞ 1729:3 1517:) 1415:e 1408:t 1401:v 1366:. 1340:. 1275:V 1255:n 1251:a 1249:( 1247:h 1243:1 1240:a 1238:( 1236:h 1234:( 1232:φ 1210:M 1205:n 1201:a 1197:1 1194:a 1192:( 1190:φ 1168:N 1161:N 1157:n 1154:a 1150:1 1147:a 1142:n 1138:x 1134:1 1131:x 1129:( 1127:φ 1123:σ 1119:M 1115:N 1111:h 1107:σ 1103:M 1099:N 1082:n 1078:b 1074:1 1071:b 1067:a 1065:( 1063:φ 1041:M 1037:N 1033:a 1028:n 1024:b 1020:1 1017:b 1013:x 1011:( 1009:φ 1005:x 964:M 960:N 955:n 951:b 947:1 944:b 940:σ 935:n 931:y 927:1 924:y 920:x 918:( 916:φ 912:M 908:N 904:M 900:N 896:σ 892:M 885:M 881:N 853:N 831:M 827:N 819:M 815:M 793:N 789:M 785:N 777:N 773:σ 769:M 765:N 761:M 757:N 753:M 749:N 745:N 741:σ 736:N 732:σ 728:M 724:N 720:M 716:N 709:M 705:N 689:. 686:) 681:n 677:a 673:, 667:, 662:1 658:a 654:( 645:M 637:) 632:n 628:a 624:, 618:, 613:1 609:a 605:( 596:N 586:M 582:N 578:n 575:a 571:1 568:a 566:( 564:φ 560:N 556:n 553:a 549:1 546:a 541:n 537:x 533:1 530:x 525:n 521:x 517:1 514:x 512:( 510:φ 506:σ 502:σ 494:M 490:N 486:M 474:N 432:Q 424:R 410:N 406:M 402:N 398:M 390:N 386:M 382:N 378:M 374:σ 366:σ 362:N 358:M 331:M 327:N 323:M 319:N 314:n 310:b 306:1 303:b 299:x 297:( 295:φ 287:M 283:N 276:M 272:N 270:( 268:h 264:M 260:N 252:M 248:N 244:h 237:N 229:M 225:M 221:N 217:M 213:N 209:N 204:n 200:a 196:1 193:a 188:n 184:a 180:1 177:a 175:( 173:φ 169:σ 165:M 157:N 153:M 145:N 136:σ 124:σ 117:N 113:M 91:) 85:( 80:) 76:( 62:. 20:)

Index

Elementarily equivalent
list of references
related reading
external links
inline citations
improve
introducing
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model theory
mathematical logic
structures
signature
first-order
σ-sentences
substructure
embedding
Ehrenfeucht–FraĂŻssĂ© games
large cardinals
rank-into-rank
complete
theory
real numbers
rational numbers
linear ordering
unbounded dense linear orderings
Ɓoƛ–Vaught test
Löwenheim–Skolem theorem
non-standard models
Peano arithmetic
signature

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