海上的大浪（這個字的起點）
這一族就是核心畫面本身，沒有任何借用。今天多半留在詩、歌詞和舊書裡，但其他所有用法都是從這裡長出去的。
noun · C2
A wave on the sea, especially a very big, rolling one.
巨浪；波濤
核心畫面
Picture the open sea lifting into one huge slow wave: the water swells up into a round back, rolls forward, and another one comes along behind it. Billow keeps that shape wherever the word travels. Smoke pushes out of a window in fat grey rolls. A curtain fills with air and swells into the room. A long skirt puffs up when the wind gets under it. Three things stay the same each time: there is a lot of it, the shape is round rather than flat, and it is swelling or moving rather than sitting still. A thin line of smoke or a flat, still sheet is not a billow.
billow 的畫面可以想成海上的大浪：水鼓起一個圓圓的背，往前滾，後面又跟著一個。這個形狀後來被借到很多東西上。煙…更多收起
billow 的畫面可以想成海上的大浪：水鼓起一個圓圓的背，往前滾，後面又跟著一個。這個形狀後來被借到很多東西上。煙一團一團翻出窗戶。窗簾被風灌得鼓進房間。長裙讓風鑽進去撐成一個弧。共通的地方大概有三個：量很大、形狀是圓鼓鼓的、而且正在鼓起或移動。細細的一條煙，或平平不動的一片布，通常就不會用這個字。From the word’s history
English took billow from Old Norse bylgja, which simply meant a wave, and the Scandinavian languages still use the same word for one today. So the sea-wave is not one meaning among several; it is where the word starts, and the smoke, cloud and cloth uses carry that wave shape over to other things.
billow 來自古諾斯語 bylgja，意思就是「浪」；丹麥語 bølge、瑞典語 bölja 到今天還是這個意思（本包提供的 Wiktionary 詞源）。所以「大浪」不是它眾多意思裡的一個，而是它的起點。煙、雲、布的用法，都是把浪的形狀搬到別的東西身上。
Wiktionary entry for billow, etymology section supplied in this packet: from Middle English *bilwe, borrowed from Old Norse bylgja, from Proto-Germanic *bulgijō; cognates Danish bølge, Swedish bölja (wave).
Three branches
一團翻滾的東西（名詞）
把浪的形狀從水搬到別的材料上：只要量大、成團、而且在翻，煙、蒸氣、塵土、大片的布都可以是一個 billow。
noun · C1
A large rounded mass of something soft, such as smoke, steam, cloud, dust or cloth, that is rolling or swelling as it moves.
一大團（煙、布等）
像浪一樣鼓起、翻湧（動詞）
名詞講的是那一團東西，動詞講的是它正在做的事：鼓起來、往外撐、一波一波地翻。核心畫面完全沒變，只是從名詞換成動作。
verb · C1
If cloth billows, the wind fills it with air, so that it swells into soft round shapes and moves in slow waves.
（布）隨風鼓起飄動