New words：

volunteer [.vɔlən'tiə]
n.志愿者；志愿兵；义务工作者；自告奋勇者
v.自愿做；义务做

Sample Sentences：

The soldier volunteered for guard duty.
They volunteered to repair the house for the old lady.

Can I have a volunteer to wash the dishes?
Volunteers were ready and waiting to pack the food in boxes.

New words：

joy [dʒɔi] n.快乐；欢乐；乐事；喜悦

Sample Sentences：

I saw the joy in her smiling face.
Learning English is my great joy.
On a hot day, a cool swim is a joy.
I felt as if my heart would burst with joy.