voluntary

adj.

1. 自愿的, 志愿的
   • He made a voluntary statement to the police.
     他自动向警方供出一切。
   • That he bumped me is voluntary.
     他故意撞了我一下。
2. 义务的, 无偿的
   • At election time the party needs a lot of voluntary helpers.
     大选时, 该党需要许多义务帮忙的人。