Some people say 'boy' or 'oh boy' in order to express feelings of excitement or admiration.
Oh boy! what resourceful children I have.
好家伙!我的孩子们多机智啊。
boys
A boy is a child who will grow up to be a man.
He was still just a boy.
他还只是个男孩。
You can refer to a young man as a boy, especially when talking about relationships between boys and girls.
the age when girls get interested in boys.
女孩儿开始对小伙子感兴趣的年纪。
Someone's boy is their son.
Eric was my cousin Edward's boy.
埃里克是我堂兄爱德华的儿子。
You can refer to a man as a boy, especially when you are talking about him in an affectionate way.
the local boy who made president.
那个当上总统的本地小伙儿。