例句：
Laughter is one of the most infectious expressions of emotion.
笑是最具感染力的情感表达方式之一。
The civil servant's expression, however, did not change, not so much as by a flicker.
然而，那位公务员的表情还是那样，丝毫没变。
I don't sing perfectly in tune, but I think I put more expression into my lyrics than a lotof other singers do.
我唱歌不是特别合拍，但我认为我唱得比其他很多歌手都更富感情。
She spoke in a quiet voice but used remarkably coarse expressions.
她说话声音很小，但是用了些特别粗俗的字眼儿。
is forms the basis for our mathematical expression for the electric field.
这是电场数学表达式的基础。