joint co-operation, mutual co-operation, co-operation

Redundancies are words that unnecessarily repeat information. Because co‑operation necessitates working with others, the modifiers joint and mutual in the familiar expressions joint co‑operation and mutual co‑operation are redundant.

• The four countries have been discussing possible co‑operation (not joint co‑operation) in the area of forest fire management.
• Their co‑operation (not mutual co‑operation) will directly affect the well-being of their citizens.