Two words that get used like synonyms, but actually are not, are inter-religious dialogue and ecumenism.
Ecumenism = the movement that fosters better understanding, promotes cooperation, and seeks reconciliation and unity among Christians.
So, for example, through such dialogue Catholics and Lutherans have had two groundbreaking events, 1) a joint statement on the doctrine of Justification by Faith in 1983 and 2) the Joint Declaration on the Doctrine of Justification on October 31, 1999.
Inter-religious dialogue = the conversations that take place between members of different world religions or different faith traditions; for example, the dialogue between Christians and Jews is inter-religious in contrast to ecumenical dialogue between Christians.
Through inter-religious dialogue Catholics and Jews have established harmonious relations that could not have been envisioned 50 years ago.
Source for definitions: Glossary of Theological Terms by Rev. John T. Ford, C.S.C.