 In other words, a \(\beta\)-reduction strategy selects, whenever a term has multiple \(\beta\)-redexes, which one should be contracted. (If a term is in \(\beta\)-normal form, then nothing is to be done, which is why we require in the definition of \(\beta\)-reduction strategy that it does not change any term in \(\beta\)-normal form.) One can represent a strategy \(S\) as a relation \(\rhd_S\) on \(\lambda\)-terms, with the understanding that \(M \rhd_S N\) provided that \(N\) is obtained from \(M\) in one step by adhering to the strategy S. When viewed as relations, strategies constitute a subrelation of \(\rhd_{\beta ,1}\).