A vane is a thin flat blade that wind or water pushes against, turning a shaft so a machine can work — the blades of a windmill, of a wind turbine, of a water wheel, of a fan inside an engine. The idea is always ‘flat piece + moving air or water + turning motion’.

A vane葉片 is a thin flat blade是一片薄而扁平的葉片 that wind or water pushes against靠風或水推動 turning a shaft讓一根軸轉動 so a machine can work好讓機器可以運作 — the blades of a windmill, of a wind turbine, of a water wheel, of a fan inside an engine像風車、風力渦輪機、水車，還有引擎裡風扇的葉片都是這樣。The idea is always這個概念永遠是 'flat piece + moving air or water + turning motion'『扁平的東西＋流動的空氣或水＋轉動』。

In careful technical English the blades of a big modern wind turbine are usually called blades, and vane is more common for smaller or older machines and for parts inside pumps and engines, but you will meet both.

In careful technical English在講究的技術英文裡 the blades of a big modern wind turbine大型現代風力渦輪機的葉片 are usually called blades通常叫做blades and vane is more common而vane比較常用 for smaller or older machines and for parts inside pumps and engines用在比較小、比較舊的機器，還有幫浦和引擎內部的零件上 but you will meet both但兩種說法你都會遇到。

The word has two other everyday uses worth knowing: a weather vane (or weathervane), the arrow or metal cockerel on a roof that turns to show wind direction — that is the oldest meaning; and the flat feathered part on each side of a feather's shaft.

The word has two other everyday uses worth knowing這個字還有兩個值得知道的日常用法 a weather vane (or weathervane)風向標（weather vane，也寫作weathervane） the arrow or metal cockerel on a roof that turns to show wind direction裝在屋頂、會轉動指示風向的箭頭或金屬公雞 — that is the oldest meaning這是最古老的意思 and the flat feathered part on each side of a feather's shaft還有羽毛軸兩側扁平的羽片部分。

It is a countable noun and sounds slightly technical or old — an ordinary conversation is more likely to say ‘blade’.

It is a countable noun這是可數名詞 and sounds slightly technical or old聽起來有點技術性或老派 — an ordinary conversation is more likely to say 'blade'一般聊天比較會說『blade』。