For questions about the study of finite or countable discrete structures, especially how to count or enumerate elements in a set (perhaps of all possibilities) or any subset. It includes questions on permutations, combinations, bijective proofs, and generating functions.

Combinatorics is the study of finite or countable discrete structures — especially enumerative combinatorics: how to count or enumerate elements in a set (perhaps of all possibilities) or any subset. This tag can be used for questions about permutations, combinations, partially ordered sets, bijection proofs, and generating functions.

Questions about:

- graph theory should be tagged with graph-theory.
- combinatorial aspects of representation theory (e.g. of the symmetric or general linear groups) should be tagged with algebraic-combinatorics and/or representation-theory. Consider also the tags: young-tableaux, characters, symmetric-groups.
- designs should be tagged with combinatorial-designs.
- analytic combinatorics should be tagged with analytic-combinatorics.
- combinatorics on words should be tagged with combinatorics-on-words.
- combinatorial optimization should be tagged with discrete-optimization.
- statistical mechanics should be tagged with statistical-mechanics.

These tags may be used alone or together with combinatorics.

To learn more about enumerative combinatorics, see Wikipedia or Richard P. Stanley's *Enumerative Combinatorics*.