帳本上真正的最後一行
這一家就是畫面本身，還沒有比喻。
noun · B2
The money a business is left with after everything has been counted — the profit it makes or the loss it takes over a period of time.
盈虧結果；淨利
核心畫面
Picture a sheet of accounts. Line after line of money coming in and money going out, all the way down the page. Then one last line at the bottom with a single number on it: what is actually left. Everything above that line is detail and argument. That final line is the part you cannot talk your way around. Every use of bottom line borrows that feeling of one last line that settles the matter.
可以想成一張帳目表。上面一行一行寫著錢進來、錢出去，一路寫到頁面最下面。最後那一行只有一個數字：真正剩下的。那一行上…更多收起
可以想成一張帳目表。上面一行一行寫著錢進來、錢出去，一路寫到頁面最下面。最後那一行只有一個數字：真正剩下的。那一行上面的全部都是細節，是可以吵的。最後那一行不能吵，它就是結果。bottom line 每一種用法，借的都是這個感覺：最下面那一行，講完就沒得談了。From the word’s history
The source explains the phrase as a reference to the literal bottom line of an income statement or other accounting record.
來源說這個詞指的就是損益表或帳目紀錄上字面的「最後一行」。所以帳本的畫面不是我們自己想的，是來源直接寫的。
English Wiktionary extract supplied in this packet (source_ref kaikki:3f6f69a190036ae4:966169359:7748)
Three branches
講話時的最後一行：真正算數的那一點
把帳本的畫面搬到對話裡。前面講的細節像帳上那些行，最後拋出來的那一句就是最下面那一行：講完就沒得爭了。
noun · B2
The one fact that matters most in a situation, or the one thing that really decides it — used when you want to push past the details and say the point plainly.
重點；關鍵的一句話
談判時自己畫的那條底線
同樣是「再往下就沒有了」的那一行，只是這次不是算出來的，是自己先定的。所以前面通常加 my、your、their。
noun · B2
The lowest price or the smallest amount that you are willing to accept in a deal, and below which you will walk away.
底線（可接受的最低條件）