字面的血
畫面本身，還沒借給任何別的東西：真的血，在真的身體裡。
noun · C2
The blood inside a person or animal, thought of as the thing that keeps them alive. This use belongs to poems and old stories rather than to everyday speech.
活命的血
核心畫面
You can think of blood moving round a body. It is not the most visible part of a person, and nobody watches it, but it has to keep moving. Stop it and everything stops with it. That is the picture the word carries: not the thing you notice, the thing you cannot do without.
可以想成血在身體裡繞著跑。它不是身上最顯眼的東西，平常也沒人在看它，但它必須一直流。一停下來，整個人就跟著停。這個字…更多收起
可以想成血在身體裡繞著跑。它不是身上最顯眼的東西，平常也沒人在看它，但它必須一直流。一停下來，整個人就跟著停。這個字帶著的就是這個畫面：不是最醒目的那個，而是少了就不行的那個。兩種用法都站在這張圖上，差別只在那具身體是真的人，還是一間店、一座城。From the word’s history
The word is simply life plus blood: the blood that life depends on. English has an older word built the same way, heart-blood.
這個字就是 life（生命）加 blood（血）拼起來的：性命所繫的那股血。英文裡還有一個用同樣方式造出來的老詞 heart-blood，意思一樣。
Wiktionary (kaikki extract, source_ref kaikki:3f6f69a190036ae4:1186586984:8372), entry 'lifeblood': From life + blood. Compare English heart-blood ('lifeblood').
Two branches
撐住一件事的命脈
把那具身體換成一間公司、一個小鎮、一段關係。血還是血，只是換成錢、客人、資訊或願意幫忙的人。
noun · C1
The one thing a business, group, place, or relationship must keep getting if it is to stay alive and keep growing — for example money, customers, information, or people who help.
命脈