Coanalytic set

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 $\boldsymbol{\Pi}^1_1$ sets (see projective hierarchy).

References

{{citation | authorlink=Alexander Kechris | author=Kechris, Alexander S. | title=Classical Descriptive Set Theory | publisher=Springer-Verlag | year=1994 | isbn=0-387-94374-9 | url-access=registration | url=https://archive.org/details/classicaldescrip0000kech }}