Glass is an amorphous solid.
It does not have a crystalline structure like many metals and ceramics.
Glass is hard but it does not undergo much plastic deformation before breaking.
When force is applied beyond its strength, glass breaks suddenly.
This property is called brittleness.
A brittle material fractures without significant permanent deformation.
Glass is not ductile because it cannot be drawn into wires.
Glass is not malleable because it cannot be hammered into thin sheets like metals.
Glass is also not generally called tough because it has poor impact resistance compared with tough materials.
Therefore, the property of glass is:
\[
\text{Brittle}.
\]