twice 
英 [twaɪs]  美 [twaɪs] 
adv. 两次；两倍

例句：
I knocked on the door twice. 

我敲了两次门。

I phoned twice a day, leaving messages with his wife. 

我一天打了两通电话，托他妻子留了口信。

Try to do this exercise at least twice a week. 

争取每天做两次这种运动。

This famous horse race has taken place here twice a year since 1310. 

自1310年以来，这项知名的赛马比赛每年在这里举行两次。

Foster, who is twice the world champion, competes today. 

两届世界冠军福斯特也参加了今天的比赛。