volunteerism
noun [ U ] mainly US uk/ˌvɒl.ənˈtɪə.rɪ.zəm/ us/ˌvɑː.lənˈtɪr.ɪ.zəm/
志愿服务，志愿主义
the practice of doing work for good causes, without being paid for it
The foundation promotes volunteerism and public service. 该基金会促进志愿服务和公共服务。