Viscosity is how thick a liquid is and how much it resists flowing. Water has low viscosity — it runs off your hand at once. Honey has high viscosity — it takes its time. That is the whole idea, and it is a measurable quantity, not just an impression: engineers give it a number, which is why you see grades like 10W-40 printed on engine oil.

Viscosity viscosity（黏度） is是指 how thick a liquid is and how much it resists flowing一種液體有多濃稠、有多不容易流動。Water水 has has low viscosity的viscosity很低 — it runs off your hand at once一碰到手馬上就流走了。Honey蜂蜜 has has high viscosity的viscosity很高 — it takes its time它會慢慢來。That is the whole idea這就是整個概念, and it is a measurable quantity而且它是一個可以測量的量, not just an impression不只是一種感覺: engineers give it a number工程師會給它一個數字, which is why you see grades like 10W-40 printed on engine oil這就是為什麼你會在機油上看到像10W-40這樣的等級標示。

Because it is a measurement word, it takes the language of measurement: viscosity increases, decreases, is high or low. Temperature is the usual thing that changes it — heat oil and its viscosity drops, cool it and the oil thickens. That single fact is behind most sentences you will meet with this word, from cooking to car maintenance to volcanoes.

Because it is a measurement word因為它是一個測量用的詞, it takes the language of measurement所以會搭配測量的語言: viscosity increases, decreases, is high or lowviscosity increases（升高）、decreases（降低）、is high or low（高或低）。Temperature溫度 is the usual thing that changes it通常是改變它的因素 — heat oil and its viscosity drops把油加熱，viscosity就會下降, cool it and the oil thickens把它冷卻，油就會變稠。That single fact這一個事實 is behind most sentences you will meet with this word就是你會遇到這個字的大多數句子背後的原因, from cooking to car maintenance to volcanoes從烹飪到汽車保養再到火山，都跟它有關。

It is usually uncountable: the viscosity of the fluid. You will sometimes see "viscosities" when several different liquids are being compared, and that is fine.

It它 is usually uncountable通常是不可數名詞: the viscosity of the fluidthe viscosity of the fluid（這液體的黏度）。You will sometimes see 'viscosities'但如果在比較好幾種不同的液體時，你有時候會看到'viscosities'這種複數形 when several different liquids are being compared, and that is fine這是沒問題的。

Outside science, people occasionally use it as a metaphor for slowness or stickiness in things that are not liquid at all — the viscosity of a bureaucracy. That is a writer's flourish, not standard use, and everyone hears the joke.

Outside science在科學之外, people occasionally use it as a metaphor人們偶爾會把它當作比喻 for slowness or stickiness in things that are not liquid at all用在完全不是液體的東西上，形容一種緩慢或黏滯的感覺 — the viscosity of a bureaucracythe viscosity of a bureaucracy（官僚體制的黏滯）。That is a writer's flourish這是一種作家式的修辭手法, not standard use不是標準用法, and everyone hears the joke而且大家都聽得出這是在開玩笑。

The adjective is viscous: a viscous liquid is one with high viscosity.

The adjective is形容詞是 viscousviscous: a viscous liquida viscous liquid（黏稠的液體） is one with high viscosity指的就是viscosity很高的液體。