a period of years(一段時期)可以定義 Decade十年, Century世紀, Millenia美年…a couple of years(兩年) 還有咩字去形容 "years"?
a hundred of years一百年Hundreds of years數百年a thousand of years 一千年Thousands of years 數千年A million of years一百萬年millions of years 數百萬年a billion of years十億年billions of years幾十億年