It is one of the 5 principles of the Paris declaration
It refers to the need for donor countries to work cooperatively, so that their actions are more harmonised, transparent, and collectively effective, as they reduce transactions costs for local partners and allow them to focus their attention on strategic concerns as opposed to the details of project management. The harmonisation agenda of the Paris declaration opens up new challenges and opportunities for CSOs and LRAs. For example, the increased emphasis on comprehensive approaches and systems-wide interventions opens up new challenges as well as opportunities on how to meaningfully engage in policy dialogue on high-level issues that affect development.
This term is directly related to the concept of coordination between donors of their activities, the exchange of lessons learned, and impact measurement and assessment, in order to improve their effectiveness.