Abschlußrelation \(\overline{R}\) einer Relation R, definiert durch \begin{eqnarray}\begin{array}{l}\overline{R}=\{(a,b):\exists \ {c}_{0},{c}_{1},\ldots,{c}_{t},t\ge 1,\\ \ \ \ \ \ \ \ \text{mit}\ \ \ a={c}_{0}R{c}_{1}R{c}_{2}R\cdots R{c}_{t-1}R{c}_{t}=b\}.\end{array}\end{eqnarray}