Substitutions rhymes with:
contributions, distributions, electrocutions, elocutions, executions, prosecution's, prosecutions, aleutians, constitution's, constitutions, contributions, distributions, electrocutions, elocutions, executions, institution's, institutions, institutions', prosecution's, prosecutions, resolution's, resolutions, revolution's, revolutions, solutions
Substitutions sounds like:
scapegoating, sebastian's, sebastianis, subjecting, subsidence, subsiding, subsistence, substance, substances, substituting, subsystems, suffocating, suppositions, suspecting