Given a finite group G, we introduce the \textit{permutability degree} of G, as Gwhere\mathcal{L}(G)isthesubgrouplatticeofGandP_G(X)thepermutizerofthesubgroupXinG,thatis,thesubgroupgeneratedbyallcyclicsubgroupsofGthatpermutewithX\in \mathcal{L}(G)$.
Source: wiktionary