Here's why:

* Boiling is the process where a liquid changes into a gas.

* Solids have a fixed shape and volume due to strong intermolecular forces holding their particles tightly together.

* To transition from a solid directly to a gas, a substance undergoes sublimation. This happens at a specific temperature called the sublimation point.

Think of it like this:

* Melting is solid to liquid.

* Boiling is liquid to gas.

* Sublimation is solid to gas.

So, instead of a boiling point, a solid has a sublimation point.