真的會割傷你的刃
刃口本身。這是字面的用法，其他兩族都從這裡長出來。
adjective · B2
So sharp that it cuts with almost no pressure, like the edge of a razor. Used about knives, teeth, claws, broken glass, grass and rock edges — anything with an edge that will cut you at a touch.
極其鋒利
核心畫面
One way to hold this word: a razor's edge held against a sheet of paper. Nobody presses. The blade only moves, and the paper is already in two pieces, with no sound and no torn fibres. Every use of the word is measuring something against that edge — no effort, no mess, an exact line.
可以想成一片剃刀的刃口貼著一張紙。沒有人用力壓。刀只是滑過去，紙就已經分成兩半。沒有聲音，邊緣也不毛。這個字的每一種…更多收起
可以想成一片剃刀的刃口貼著一張紙。沒有人用力壓。刀只是滑過去，紙就已經分成兩半。沒有聲音，邊緣也不毛。這個字的每一種用法，都是拿東西去跟那個刃口比。比的是三件事：不費力、不拖泥帶水、留下一條準確的線。看懂這三件事，牙齒、頭腦和西裝為什麼能用同一個字，就說得通了。Three branches
把刃搬到頭腦上
同一個刃口，這次切的是問題。跟過來的是「不費力」和「準」這兩點。
adjective · B2
Able to think and understand very quickly, and to notice the small thing everyone else missed. Used about a person's mind, memory, wit or judgement.
思路敏銳
把刃變成看得見的線條
這一族取的不是「會割人」，而是刃口留下的那條乾淨線。所以它形容的是外型的精準。
adjective · C1
Looking very neat and stylish, with clean straight lines and nothing out of place. Used about clothes, a suit, a haircut, or the whole way someone is dressed.
俐落有型