noun

the process or result of joining two or more things together to form a single entity.

the election results produced pressure for fusion of the parties

blend,blending,combination,amalgamation,joining,bonding,binding,merging,melding,mingling,integration,intermixture,intermingling,synthesis,coalescence,compounding,agglutination,uniting,marrying,alliance,unification,commingling,commixture,interflow