郭敦顒回答：
Volunteer——n,志愿者.
Voluntary——a,自愿的,义务的.
上星期日,我和同学们到公园清扫垃圾,大家都做了志愿的清洁工.
Last Sunday, my classmates and I to the park for collecting refuse, we all do the volunteer cleaners.
Volunteer,也可用voluntary代替.