Let GG be a and let SGS\subseteq G. One says that SS generates GG (or that SS is a generating set) if the smallest of GG containing SS is all of GG, i.e.

S=G,\langle S\rangle = G,

where S\langle S\rangle denotes the by SS.

Equivalent characterizations

Equivalently, every element of GG can be written as a finite product of elements of SS and their inverses.

Remarks

Generating sets are the input data for , and finiteness of generating sets is a basic measure of complexity.

Examples
  • Z\mathbb{Z} is generated by {1}\{1\} under addition.
  • Cn=aC_n=\langle a\rangle is generated by any element of order nn.
  • S3S_3 is generated by {(12),(123)}\{(12),(123)\} (many other generating sets exist).