Voluntary actions or activities are done because someone chooses to do them and not because they have been forced to do them.
mandatory
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。
The scheme, due to begin next month, will be voluntary.
此项目为自愿参加并将在下个月开始。
Voluntary work is done by people who are not paid for it, but who do it because they want to do it.
In her spare time she does voluntary work.
她利用业余时间做义工。
He'd been working at the local hostel for homeless people on a voluntary basis.
他曾在当地的救助站做义工,帮助无家可归者。
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.
Some voluntary organizations run workshops for disabled people.
一些志愿组织为残障人士开办讲习班。