名單最上面那一格：最好、最重要、最先
這一組直接用核心畫面：有一張排好的名單，而它指著最上面那一格。名詞用法講「那一個」，形容詞用法則把那一格貼到名詞上。
noun · B1
The best, most important, or most successful person or thing in a group — the one that is ranked first, or the person who is in charge of it.
第一名／最重要的那個
核心畫面
One way to hold number one: picture a list with everyone and everything set out in order, and the very top row marked 1. The list can be a world ranking, a sales chart, the jobs in a company, or just the things you have to do this morning. Whoever or whatever sits in that 1 row is the one put in front of all the others. From there the word grows two ways at once — toward best and most important, and toward first and do it before the rest. Sometimes, though, the 1 is not a ranking at all but simply a label: the 1 on the back of a shirt, or the 1 that adults and small children use so they do not have to say a word out loud. In those uses the number marks a place, not a height.
「number one」可以想成一張把大家排好的名單，最上面那一格寫著 1。名單可能是世界排名、銷售榜、公司的職位，…更多收起
「number one」可以想成一張把大家排好的名單，最上面那一格寫著 1。名單可能是世界排名、銷售榜、公司的職位，也可能只是今天早上要做的幾件事。站在 1 號那一格的，就是被放到所有人前面的那一個。從這裡出發，它同時往兩個方向長：一邊是「最強、最重要」，一邊是「第一個、先做」。不過有時候那個 1 不是名次，只是一個編號——球衣背後的 1 號，或是大人跟小孩之間的 1 號——這時候它標的是位置，不是高低。From the word’s history
Wiktionary records number one as a piecewise doublet of numero uno: number matches numero and one matches uno, so the two expressions are the same phrase built out of different word stock. That fits the picture above — both of them simply name the spot marked 1.
來源資料記到，英文的 number one 和外來的 numero uno 是逐字對應的兩種說法：number 對 numero，one 對 uno。也就是說，同一句話用兩套詞彙各講了一次。這剛好跟上面的畫面對得起來——兩個說法都只是在叫「標著 1 的那一格」。
Wiktionary entry for 'number one' (packet source_ref kaikki:3f6f69a190036ae4:1173915670): etymology_text 'Piecewise doublet of numero uno.'
Five branches
排行榜上的那首歌
排行榜就是一張每週重排一次的名單，1 號那一格輪流換人；這裡的特別之處是那一格上的東西具體到可以數。
noun · B1
A song or record that is at the top of the music charts in a particular period because more people bought or played it than anything else; also that top position itself.
冠軍單曲／排行榜第一
球衣上的 1 號
一樣是「1 號那一格」，但這一格是位置編號，不是名次；只是球隊裡的 1 號通常也是先發、第一選擇，所以又跟「最好」沾上邊。
noun · B2
In a team sport where players carry numbers, the player who holds the number 1 spot — in soccer the main goalkeeper, who wears the number 1 shirt, and in cricket the batter who goes in first.
一號球員（足球守門員／板球開局打者）
把 1 號留給自己
同一張名單，只是排名單的人把自己寫在第一行；這是一個教學上的連結，不是說它在歷史上由「第一名」變過來的。
noun · B2
If you look out for number one, you take care of yourself and your own interests first and do not worry much about other people. It often sounds selfish.
只顧自己
不想講出口，就給它一個號碼
這一格跟高低完全無關，只是拿數字當代號；把它放在同一張圖裡是為了好記，不是說它從「第一名」變過來的。
noun · B1
A polite, indirect word for urine, or for the act of urinating, used especially when talking with young children.
小號（尿尿）