You owe a certain person a sum of money.

你欠着某人一笔钱。

He did her out of a sum of money.

他骗了她一笔钱。

He is saving a sum of money to buy a home for his family.

他正在攒钱为家人买房子。

Enclosed you will find a sum of money.

你会在信封里找到一笔钱。

He has put aside quite a sum of money.

他已经存了相当大一笔钱。