 Proposition 1.1. If \({\mathcal{M}}\) is compositional, then for all phrases \(e,e'\) and all contexts \(C\blbr\):   \[\tag{1}\label{compositionality}{e \simeq_{\mathcal{M}} e'} \Rightarrow {C[e] \simeq_{\mathcal{M}} C[e']}.\]