zero degrees

[fadysandy]

This example is in 'Oxford Advanced English Dictionary'
'Water freezes at zero degrees Celsius.'
Why can we use plural 'degrees' with 'zero' singular?

 

[Roman55]

I am not a teacher.

How many degrees are there when the temperature is 0°C?

There are none. There are no degrees.

Not only can we use the plural, we must use the plural.

 

[Rover_KE]

We only use the singular after 1. After every other numerical value we use the plural.

0.001 degrees/miles/grams etc.
minus (negative) 1.1 inches/metres/kilograms etc.

 

[Matthew Wai]

We only use the singular after 1.

Is minus 1 also singular?

 

[SoothingDave]

Is minus 1 also singular?

Yes.

 

[Matthew Wai]

We only use the singular after 1.

My dictionary says "singular...refers to one...". Is it the reason why only "one" is singular?