Typical window glass is officially classed as amorphous solid. That means that it solidifies without crystallizing, which means that it doesn't have a clear transition point at which it turns from liquid to solid, it just becomes more and more viscous until it stops flowing all together.
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Glass is not a liquid in the strictest sense of the word. But it is also not a standard solid. The chemistry of glass is complex.
Typical window glass is officially classed as amorphous solid. That means that it solidifies without crystallizing, which means that it doesn't have a clear transition point at which it turns from liquid to solid, it just becomes more and more viscous until it stops flowing all together.