有一读者问：有这样一个句子：
(1)No matter how complex, all machines are combination of simpler machines such as the lever, the pulley, and the inclined plane.
为什么 No matter how complex 之后没有主语和谓语？它能说是一个状语从句吗？
No matter how complex 是一种省略结构，相当于 No matter how complex they may be, 所以还是一种状语从句，表示让步。这种省略结构并不罕见，再如：
(2)He had grown accustomed to sleeping soundly on any bed no matter how hard or uneven . （no matter how hard or uneven 是一省略结构，=no matter how hard or uneven it might be）
有时这种省略结构只省去连系动词，如：
(3)She set her lips and determined to pull through no matter how hard the ride or how long the fast . （the ride 与 the fast 之后皆省去 was）
顺便指出，与 no matter how 同义的 however 亦可后面只跟一形容词或相当于形容词的过去分词，如：
(4)What he needed tonight was total escape. A detective story, however bizarre , however removed from the actualities of detection, was the last thing to give it to him. （ 第一个 however 之后接形容词 bizzarre, 第二个 however 之后接过去分词 removed）
