n.

1. 协会，公会，社团[C]
   Have you joined the teachers' association?

   你加入教师协会了吗？

2. 联盟[C]
3. 联合，结合；交往[U][（+with）]
   I benefited much from my association with him.

   我跟他的交往中获益匪浅。

4. 联想，联想物[C][U]
   What association do you have with the color green?

   绿色会使你产生什么联想？

5. 伙伴关系[U]

n.

1. a group of people organized for a joint purpose.
2. a connection or cooperative link between people or organizations.
   ▸Chemistry  a weak interaction between molecules, such as hydrogen bonding.
3. a conceptual connection.
4. Ecology  a stable plant community including a characteristic group of dominant plant species.