Here's what rhymes with interrelationship.

Consider these alternatives

interrelations / relations interrelation / relation interdependencies / tendencies interrelatedness / relatedness byplay / they congruity / continuity incongruity / perpetuity interplay / they homologies / qualities symbiotic / logic correlations / relations interconversion / person formalise / normalise intercessor / never illumine / human disjunction / function intractability / stability betweeen / between synchronisation / information predicates / states covariances / variances