Glass is unusual in that it is an amorphous body. Silicon dioxide molecules do not form an ordered structure. Glass cools so quickly that when it goes from liquid to a "solid" state, the molecules don't have time to line up in an ordered crystalline structure. What makes glass visually hard is atoms or molecules that are chemically bonded so strongly to each other that they cannot slip next to each other. However, the lack of an ordered crystal structure makes glass still liquid, even when it is in a visually solid state. It is precisely because glass is actually liquid that in window frames in old houses, where windows have stood for several decades, it is clearly noticeable that the glass is thinner at the top than at the bottom. This is due to the fact that some of the glass has already been glass from top to bottom over the years. Therefore, in such houses, the windows rattle in the frames, because at the top they are already thinner than the gap prepared for them. Sometimes this effect is so noticeable that even a gap is formed on top.
Hardness and plasticity have no absolute value, but only a relative one. And all bodies are actually liquid and solid at the same time. When there is a huge mass and strength in the case, the difference loses its meaning. The rigid definitions we create for ourselves lead to misconceptions and viscous rumors.