(plural commutator lengths)
- The number of multiplicands needed, at a minimum, to express a given group element as a product of commutators.
- In , the commutator length of is two, since it equals but isn't a commutator.
- The supremum, over all elements of a given group's derived subgroup, of their commutator lengths.
- The commutator length of is at least two, since there's an element of commutator length two in it.