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Relations may be inputted in a number of ways. Relations may be separated by newlines or semicolons. A single relation is something which is equal to the identity (such as ij^-1k), though for shorthand they may have an equals sign, as in the case of ij=k; jk=i; ki=j. Exponents for generators are not parenthesized, so x^-22y^1 is valid and correct. The symbol 1 is the identity element. Parts of relations may be parenthesized, for instance (ab)^2 to represent abab.

The subgroup H may be generated by any collection of elements from G. It does not need to be a normal subgroup. The list of generators contains all of the generators for H as well, so take care that this subgroup does not contain generators not present in G, otherwise the resulting index [G:H] is likely infinite.

Normality detection is accomplished by considering the covering space corresponding to H and checking that the group of deck transforms is transitive on the fiber of the base point (see Proposition 1.39 in Hatcher). In particular, it checks for each generator that there is a deck transform which carries a lift of the base point along a lift of the generator.