烘焙裡的發酵
這一組就是核心畫面本身，名詞指那一小撮東西，動詞指把它拌進去、讓麵團脹起來的動作。
noun · C1
A substance, usually yeast, that is mixed into flour and water so that the dough fills with gas, swells, and can be baked into soft bread.
發酵劑、酵種
核心畫面
Leaven can be pictured as a pinch of something alive dropped into a big, heavy lump of dough. You can hardly see it, and yet it does not stay where it was put: it works out through the whole mass, filling it with air. What was dense and flat becomes light and full, and there is no part of the dough it has not reached. Two things in that picture are doing the work — a very small amount changes a very large thing, and the change goes everywhere.
「leaven」可以想成一小撮活的東西，被丟進一大團又重又硬的麵團裡。它小到幾乎看不見，卻不會待在原地：它會一路走遍…更多收起
「leaven」可以想成一小撮活的東西，被丟進一大團又重又硬的麵團裡。它小到幾乎看不見，卻不會待在原地：它會一路走遍整團，把空氣填進去。本來又沉又扁的，變得又輕又飽滿，而且沒有一個角落是它沒到過的。這個畫面裡有兩件事在出力——很少的份量改變很大的東西，而且改變是走遍全部的。From the word’s history
The etymology tree in our source traces leaven through Middle English levayn and Old French levain back to Vulgar Latin *levamen, from Latin levo 'to raise' and levis 'light'. The root idea of lifting and lightening sits under every use of the word.
我們手上的字源樹把 leaven 一路追到中古英文 levayn、古法文 levain，再到通俗拉丁文 *levāmen，源頭是拉丁文 levō（舉起）和 levis（輕）。「抬起來、變輕」這個根，正好撐著這個字所有的用法。
Wiktionary etymology tree for leaven, supplied in this evidence packet (kaikki:3f6f69a190036ae4:456379704:24088)
Three branches
讓沉重的場合變輕
沉悶的場合就像那團又重又扁的麵團，加進一點輕的東西，整個就被抬起來一些——借的是字根裡「舉起、變輕」那一半。
verb · C2
To put something into a serious, dull or sad situation that makes it lighter and easier to take.
調和、使輕鬆一些
一點點滲透、把整體改掉
這一組借的是核心畫面的另一半：不是「變輕」，而是「份量很少卻走遍全部」，所以方向可好可壞。
noun · C2
A small influence that spreads through a whole group or a whole person and changes it — in the older writing where this use is found, most often for the worse.
潛移默化的影響（常指變質）