QUANT-PLURAL
大量；无数
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.
例句
Biological systems have been doing this for billions of years...
生物系统亿万年来一直都是这样。
He urged US executives to invest billions of dollars in his country.
他力劝美国公司的高管们向他的国家投资数十亿美元。