What is the difference between glass and glasses?

Answer 1

The noun "glass" is an uncountable noun as a word for a substance.

• Glass made into sheets for windows, picture frames, etc. is a non-count noun; units are sheets of glass, panes of glass, or pieces of glass.
• Glass formed into objects such as ornaments, decorations, jewelry, etc., is used as an attributive noun (a noun used as an adjective); the noun it describes is countable; for example a glass bead or glass beads, a glass bottle or glass bottles.

The plural noun "glasses" is used when there are multiple types of glass, for example, "various glasses within igneous rocks".

• The noun "glasses" is the plural form of the noun for a beverage container, for example, a glass of water or two glasses of water.
• The noun "glasses" is an uncountable noun as a word for spectacles, a shortened form of "a pair of glasses" or "two pairs of glasses".