1. 自愿的;志愿的;主动的;自发的
    Voluntary actions or activities are done because someone chooses to do them and not because they have been forced to do them.

    e.g. Attention is drawn to a special voluntary course in Commercial French...
           一门特别的商务法语选修课引起了大家的关注。
    e.g. The scheme, due to begin next month, will be voluntary.
           定于下个月开始实施的方案是自愿性质的。

2. （工作）无偿的，义务性的
    Voluntary work is done by people who are not paid for it, but who do it because they want to do it.

voluntary的意思

    e.g. In her spare time she does voluntary work...
           她在业余时间做义工。
    e.g. He'd been working at the local hostel for the handicapped on a voluntary basis.
           他曾在当地的残疾人救助站当过义工。

3. （工作者）志愿的,无偿服务的
    A voluntary worker is someone who does work without being paid for it, because they want to do it.

    e.g. Apna Arts has achieved more with voluntary workers in three years than most organisations with paid workers have achieved in ten...
           “我们”艺术中心依靠志愿者在3年内取得的成就超过了大多数雇用受薪员工的机构10年中取得的成绩。
    e.g. We depend solely upon our voluntary helpers.
           我们完全依靠我们的志愿者。

4. （机构或组织）志愿的，义务性的
    A voluntary organization is controlled and organized by the people who have chosen to work for it, often without being paid, rather than receiving help or money from the government.

voluntary的近义词

    e.g. Some local authorities and voluntary organizations also run workshops for disabled people...
           一些当地机构和志愿组织也为残疾人开设了一些工场。
    e.g. It has been largely through the voluntary sector that the needs of victims have been met.
           受害者的需要主要是通过志愿组织予以满足的。