billions
A billion is a thousand million.
The Ethiopian foreign debt stands at 3 billion dollars.
埃塞俄比亚的外债达30亿美元。
Billions means a very large number or amount of something.
He thought that it must be worth billions.
他认为它一定值亿万元。
If you talk about billions of people or things, you mean that there is a very large number of them but you do not know or do not want to say exactly how many.
Biological systems have been doing this for billions of years.
生物系统亿万年来都在这样做。