附在表面的那一層
核心畫面的「結果」那一面：你看得到、摸得到、甚至刮得下來的那層東西。
noun · C2
A layer of a substance that slowly builds up on the surface of something over a long time.
積層／慢慢附上的一層
核心畫面
One way to hold this word: something gets bigger by having things stick to the outside of it, a little at a time. Rust on a key left in a river, shells on a hull, a new clause added to a rule every few years, dust drawn together into a planet. Nothing grows from within; everything arrives from outside and stays.
accretion 的核心畫面可以想成「東西從外面黏上來，所以變大」。丟在河裡的鑰匙長出一層鏽。船底黏上一層貝殼。規…更多收起
accretion 的核心畫面可以想成「東西從外面黏上來，所以變大」。丟在河裡的鑰匙長出一層鏽。船底黏上一層貝殼。規章每隔幾年多加一條。宇宙裡的塵埃互相吸住，滾成一顆行星。共同點有兩個。一是從外面加上來，不是從裡面長出來。二是慢，一次只加一點點。From the word’s history
A learned borrowing from Latin accretio, from accresco (ac-, towards + cresco, to grow), the same root as increase and crescent.
Wiktionary 記它借自拉丁文 accrētiō，來自 accrēscō：ac-（朝向）加 crēscō（生長、增加），跟 increase、crescent 同一個根。所以「朝著變大」是這個字最老的意思，今天不管講鏽層、講制度、還是講行星，底下都是同一個動作。
Wiktionary 'accretion' etymology (kaikki extract, source_ref kaikki:3f6f69a190036ae4:63869907:99623)
Two branches
一點一點加上去的過程
核心畫面的「動作」那一面：不看最後那層，看它是怎麼一次一點疊起來的。
noun · C2
A slow process in which new things are added one after another, so that something gradually grows bigger or changes.
逐漸累加／漸進形成