The right way to say -40℃ ?

Ah，I forgot to post this version: 40 centigrade below zero!

Both are commonly used . Like Shining I prefer 40 { degrees } below zero .I haven't seen 40 centigrade below zero ever been used .

Thank you very much~ Got it ^^

oh, but the C is usually 'Celsius', as opposed to F for 'Fahrenheit'.

This might help (I just looked it up ... and learned something new! haha).
http://adsabs.harvard.edu/abs/1962Sci...136..254S

Oh, yeah, Blue is correct, sometimes we don't say 'degrees'.

conversationally, we would say "It's minus forty" - we'd only use "It's minus forty Celsius" if we needed to specify the scale - since -40 is about the same in both Fahrenheit and Celsius, we wouldn't need to specify it.

Wow, I never know that -40 is about the same in both Fahrenheit and Celsius. But we always don't use Fahrenheit in China. So for the most of time, I don't need to specify the scale.
Then to sum up, -40℃ can be called "40 (degrees) below", "minus forty", or "minus 40 Celsius".

Thank you all ^^

Mark and Rachel .

I know if is only a technical point every country in the world { as far as I know uses the centigrade scale for measuring temperature .

40 degrees centigrade was in common use during the transition periad between the farenheit scale and centigrade scale .ure .

We would now call 40 degre centigrate " over kill "which means overstating . But it as not wrong to use it . If translating old texts it would be good to find out which scale was being used at that time .,

If it was Farenhiet,say fareihiet or much better do a calculation between farenfeit and the cntigrade scale and use write as centigade .

Phil .

In fact, I don't know much about Farenheit, I can't convert Celsius into Farenheit. And it confused me a lot when my American friend told me that it was very hot there, the temperature rose to more than 115(well, i forget the exact figure, because I fail to convert it into celsius.)
hehe, I need to learn more. (And thank you for teaching me centigrade, celsius, and farenheit) *^o^*

America has not converted liquid mesuurement from gallons to litres so it does nor surpise me that they are stll using FARENHIET for temperature . ) From memory 32 degrees fanenhiet is zero degree centigrate, .

Got it~ o(.".)o

A helpful conversion table:
Fahrenheit-->Celsius/Centigrade
32F-->0C
(now keep adding 18 to the F column and 10 to the C column):
50F-->10C
68F-->20C
86F-->30C
98F-->40C

The actual conversion formulas (if you're interested) are these:
°F to °C: Subtract 32, then divide by 9, and then multiply by 5
Example: 70°F: 70-32=38, 38/9=4.2 4.3x5=21°C

°C to °F: Divide by 5, then multiply by 9, and then then add 32
Example: 25°C: 25/5=5, 5x9=45, 45+32=77°F

Note: I am using the decimal point, not the European decimal comma.

Wow, very informative!!! I learnt a lot of new things!!! ^^
I know decimal point, it's "." , right? But what is the European decimal comma? What's the difference between them?

Ps: For 38/9=4.2 4.3x5=21°C, isn't it "4.2x5=21°C" ?

In Europe, instead of writing 21.5 they write 21,5 ... so I have to be careful when I write to my European friends :)

I don't understand your conversion...
you forgot to subtract 32!!!

38°F is definitely not 21°C, it should be very close to 0°C. Here is the conversion:
38°F: subtract 32: 38-32=6, divide by 9: 6/9=0.67, multiply by 5: 0.67x5=3.35°C

But I understood yours ~lol~
I mean that there was a typo in your example:
70°F: 70-32=38, 38/9=4.2, 4.3x5=21°C

For this: 38/9=4.222222
So 4.3 is wrong, it should be replaced by 4.2
And then multiply by 5: 4.2x5=21°C

I've been splitting hairs, haven't I?
Sorry~~~~(>_<)~~~~
And thank you for explain once more ^^

Oops... my table had a mistake. Sorry!!!
Here is the correct table

Fahrenheit-->Celsius/Centigrade
32F-->0C
(now keep adding 18 to the F column and 10 to the C column):
50F-->10C
68F-->20C
86F-->30C
104F-->40C <--- I corrected this line!!!

Oh, I see... I was doing math in my head, so I confused 4.2 with 4.3. You are right: 4.3 is wrong.
Nice catch! (we say this in America when somebody "catches" a mistake that another person made) :-)

そうか。
So I was a catcher, right?
Thank you for the "nice catch" explanation~^ ^~

Here is another expression: "eagle eyes"
At work, I pay attention to detail, so I often "catch" mistakes that my coworkers make on calculations. My colleagues say that I have "eagle eyes" (I have very good vision, like an eagle).

So, when you caught my mistakes, you showed that you too have "eagle eyes" :))

Rachel Qさんは日本語も勉強していますか？

Haha, nice teacher ^^ I have eagle eyes as you~
2か月に日本語が勉強しました。少し話せます,とても苦手ですよ。今,日本語の時間がなって,勉強していないよ。英語がいつも一生懸命勉強しているよ。
Hope I can pick up Japanese later! But I just don't have time now! ~~~~(>_<)~~~~ What a pity!

Rachel Qさんはとても上手に日本語で書きますよ！

Haha, where where!!!(It's the Chinese way to be modest--哪里哪里, like まだまだ in Japanese).

Wow, it comes as a great surprise to learn that centigrade is so rarely used. I suppose that most Chinese would feel confused about Celsius, while very clear on centigrade. Why have we always been taught such uncommon words?…?_?… I wonder…

It's just the word "Centigrade" isn't used anymore. It was changed to Celsius in 1948 to avoid confusion with another measurement.

Hehe, I've learnt from the website that agreva3 posted. This is new to me~
Thnx (*^__^*) ……

Officially, "Centigrade" is not used anymore, but some countries still use it, so it's good to know that "Centigrade" and "Celsius" refer to the same temperature scale :)

Emmmmm! ^^

A very helpful summarization ^^ Thnx~