zero degrees (Celsius); freezing point
Primarily refers to 0°C, the temperature at which water freezes. Often used in weather contexts.
The temperature this morning was zero degrees.
Can be used for zero on any scale, but most commonly refers to temperature. For other scales, context makes the meaning clear.
Water freezes at zero degrees.
The needle of this gauge is pointing to zero.
零度 is the everyday term for zero degrees Celsius, whereas 零点 is a more technical way to refer to that same zero point on a scale.
absolute zero
Compound of 零 (rei, 'zero') and 度 (do, 'degree').