Piece in small cancellation theory (source code)

= Piece in small cancellation theory

= Small cancellation piece
{synonym}

A piece is a nontrivial combinatorial path that occurs in two essentially distinct positions on oriented cell attaching paths. These may be different cells or distinct admissible occurrences on one attaching path; occurrences identified by the defining attaching-path symmetry are not counted twice. In a symmetrized <group presentation>, it is a common initial segment of distinct <relator> words. Internal arcs of a <reduced disc diagram> are pieces, because otherwise the neighboring cells form a cancellable pair.