cooperator

基本解释

So long as you think of yourself alone, you cannot be a good cooperator.
如果总想着自己，你就不能成为一名好社员。
The foreign cooperator shall send a certain number of teachers from its own educational institution to teach in the Chinese-foreign cooperatively-run school.
外方合作办学者应当从本教育机构中选派一定数量的教师到中外合作办学机构任教。
Article 10 A Chinese or foreign cooperator in running a school may contribute with funds, in kind or in forms of land-use right, intellectual property rights or other assets to establish the school.
第十条中外合作办学者可以用资金、实物、土地使用权、知识产权以及其他财产作为办学投入。

Then there is the relationship between the cooperator and the person against whom they testify.
FORBES: Why do people have a negative view of cooperators?
The life of a government cooperator is not an easy one but it does have benefits when it comes to reducing prison time.
FORBES: Connect
In addition, you have the personal circumstance of the cooperator.
FORBES: Why do people have a negative view of cooperators?