lifeblood
n. 生机的根源；生命必须的血液；命脉；命根子
例句
Tourism is the lifeblood of the city.
旅游业是这座城市的命脉。
《牛津词典》
Coal and steel were the region's lifeblood.
煤炭和钢铁曾是这个地区的生命线。
《柯林斯英汉双解大词典》
Trade is the lifeblood of most modern states.
贸易是大多数现代国家的命脉。
