Definition
For every ordinal ''η'', a cardinal κ is called η-extendible if for some ordinal ''λ'' there is a nontrivialVariants and relation to other cardinals
A cardinal ''κ'' is called ''η-C(n)''-extendible if there is an elementary embedding ''j'' witnessing that ''κ'' is ''η''-extendible (that is, ''j'' is elementary from ''Vκ+η'' to some ''Vλ'' with critical point ''κ'') such that furthermore, ''Vj(κ)'' is ''Σn''-correct in ''V''. That is, for every ''Σn'' formula ''φ'', ''φ'' holds in ''Vj(κ)'' if and only if ''φ'' holds in ''V''. A cardinal ''κ'' is said to be C(n)-extendible if it is ''η-C(n)''-extendible for every ordinal ''η''. Every extendible cardinal is ''C(1)''-extendible, but for ''n≥1'', the least ''C(n)''-extendible cardinal is never ''C(n+1)''-extendible (Bagaria 2011). Vopěnka's principle implies the existence of extendible cardinals; in fact, Vopěnka's principle (for definable classes) is equivalent to the existence of ''C(n)''-extendible cardinals for all ''n'' (Bagaria 2011). All extendible cardinals are supercompact cardinals (Kanamori 2003).See also
* List of large cardinal properties * Reinhardt cardinalReferences
* * * * Large cardinals {{settheory-stub