external qi外气externaladj.外来的；外部的；外面的；表面的n.外观；外部；外界事物external attribute外部属性external conductor外导体external beam path外束路线external digestion体外消化external diffusion外扩散external ballistic外弹道external component外元件external drip feed滴油润滑器external expansion对外扩张externally bolting体外栓接

1. The activity of traffic gives advantage to the society, but at the same time it also brings some adverse effects, which produce the exterior cost of traffic.
   摘要交通活动给人们的生活提供了便利，同时也给自然环境和社会带来一定的负面影响，即产生了交通的外部成本。