Definition 1. A set $X$ is inductive if
\[\forall x \in X : x \cup \{x\} \in X.\]References
- [1]
- Eric W. Weisstein, with contributions by Margherita Barile. Inductive Set. MathWorld – A Wolfram Resource. Accessed Sep 14, 2026.
- [2]
- Thomas Jech. Set Theory. 3rd Millennium ed, rev. and expanded. Springer, 2002. p. 12.