lifeblood
/ˈlaɪfblʌd/noun
mass noun
1- poetic/literary the blood, as being necessary to life〈诗/文〉血液。
1.1
- figurative the indispensable factor or influence that gives something its strength and vitality〈喻〉生命线, 命根子：
the movement of coal was the lifeblood of British railways.
煤炭运输是英国铁路的命脉。