An induced forest of a graph is a vertex-induced subgraph that is a forest. Thus a subset of the vertex
set
determines an induced forest precisely when
contains no graph cycle.
For a finite simple graph, the complementary vertex set is then a feedback
vertex set. Consequently, the maximum number of vertices in an induced forest is the vertex
count minus the feedback vertex set number.
The Albertson-Berman conjecture concerned
the size of the largest induced forest in a planar graph
(Cames van Batenburg et al. 2026).
The induced forest polynomial counts induced forests by their number of vertices.