Coanalytic set

• abstract: In the mathematical discipline of descriptive set theory, a coanalytic set is a set (typically a set of real numbers or more generally a subset of a Polish space) that is the complement of an analytic set (Kechris 1994:87). Coanalytic sets are also referred to as \scriptstyle\boldsymbol{\Pi}^1_1 sets (see projective hierarchy).

以上来源于: WordNet