List coloring of a finite simple graph is a proper coloring in which the color of each graph vertex is chosen from a prescribed finite set of available colors, called its list. The lists may differ from one graph vertex to another (Dvorák and Postle 2018).
For a nonnegative integer , a graph is
-choosable iff every assignment of
lists with
colors in each list admits a list coloring. The least such
is its choice number, also
called its list chromatic number (Gu and Xu 2026, p. 1).