1）将数词当作名词看待，当表示多个某一数字时，基数词可用复数形式。如：
Four twos make eight.
4乘以2等于8。
How many twos are there in ten?
10里面有几个2？
The soldiers marched in tens.
士兵们10人一排前进。
2）逢整“十”的基数词若用复数形式，可以表示某人的大约年岁和世纪中的年代。如：
Long hair for men came in the sixties.
男子留长发在20世纪60年代很流行。
He was in and out of jail for most of his twenties.
他二十几岁时几乎一直频繁进出监狱。
Great changes took place in China in the1980/1980.
二十世纪八十年代，中国发生了巨大变化。
I am in my fifties.
我五十多了。
注：若表示“十几岁”，则用teens。如：
His parents divorced during his teens.
他父母在他十几岁时离婚了。
3）当 hundred， thousand等表数百、数千、成千上万等意义时。如
Millions of Students paid attention to the state affairs.
数百万学生关心国家大事。
Hundreds of people joined in this argument in the small town.
在这个小镇上就有数百人参加这场争论
若 hundred of等之前有 several，many等修饰时， hundred用复数或单数皆可。
Several hundreds of houses were burnt down in the fire.
几百幢房屋在这场大火中被烧毁。
3）某些惯用表达中，基数词习惯上用复数形式，如：
at sixes and sevens 乱七八糟，不和睦
We have only just moved into the house, and everything is at sixesand sevens.
我们刚搬进这栋房子，一切是乱七八糟的
by/ in twos and threes 三三两两地
The people came in /by twos and threes.
人们三三两两地进来了。
by twos 两个两个地
They went out by twos.
他们两个两个地走出去。
by ones and twos 三三两两地
People began to leave the auditorium by ones and twos.
人们开始三三两两地离开大礼堂。
be dressed up to the nines 打扮得很华丽
on all fours 在地上爬