1) double（前面不用任何冠词）直接加在一个定指（常常有 the）的数量前面，当中不要再加介词；合在一起形成另一个双倍大的新数量，可以当作名词成分。

• China's share of world trade in 2002 was almost double the 2.7 percent of world trade China carried just seven years earlier. (Washington Quarterly, Winter 2003- 2004, p.77)中国在世界贸易中所占的份额，到 2002 年竟双倍于中国短短七年前在世界贸易中所占的百分之二点七。

这个新数量，前面还可以加上介词。

• Both sets of laboratory animals had lived healthily for double their lifespans after receiving shots of the formula.两组实验动物，在受到了制剂的注射后，健健康康地活过了双倍于自己寿命期的时间。
• Peripheral Artery Disease (P. A. D.) is often described as poor leg circulation, which puts you at double the risk of heart attack or stroke. (US News & World Report, July 21-28, 2008, p.7, Plavix advertisement)外周动脉病常常说是腿部血流不畅，它双倍增加了你心脏病发作或中风的危险。

2) double 还可以有副词 doubly，可以放在形容词前面表示该情状的双倍。

• It (Bush's veto of stem cell research funding bill) was doubly disappointing to advocates of embryonic stem cell research in New York...布什的否决，对于纽约州主张进行胚胎干细胞研究的人们来说，更是加倍地使人失望…