Solid condensation on a surface below 0 degrees Celsius is known as frost.

Here's why:

* Condensation: This refers to the process where water vapor in the air changes into liquid water.

* Below 0 degrees Celsius: This is the freezing point of water, meaning that the water vapor will directly change into solid ice crystals instead of liquid water.

* Frost: This is the name given to the layer of ice crystals formed by this direct condensation of water vapor onto a surface below freezing.

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