Advanced batteries are moving out of specialized markets and creeping into the mainstream, signaling a tipping point for forward-looking technologies such as electric cars and rooftop solar panels.
出自-2016年12月閱讀原文
柯林斯高階英漢雙解學習詞典釋義
N-COUNT
（外部的）屋頂
A rooftop is the outside part of the roof of a building.