Plural of Glass

The Quick Answer

When refering to the material, glass is a mass noun.

When refering to a drinking container, the plural is glasses.

The Plural of Glass

When refering to the material, glass is a mass noun. For example:

Multi-storey buildings are frequently constructed with walls made almost entirely of glass.
In early 17th century England, glass became common in the windows of ordinary homes.

When refering to a drinking container, the plural is glasses. For example:

While we may not need eight glasses a day, there are plenty of reasons to drink water.
My grandmother is over eighty and still doesn't need glasses. She drinks right out of the bottle. (Henny Youngman)

The table below shows the standard rules for forming the plurals of nouns in English.

Type	Example of Type	Forming the Plural	Plural
Most Nouns	cat scythe	add s	cat scythes
Noun Ending s, sh, ch, x or z	glass dress	add es	glasses dresses
Nouns ending [consonant] o	mango zero tomato	add either s or es (There are no rules for this - you have to know.)	mangoes or mangos zeros tomatoes
Nouns ending [vowel] o	patio ratio	add s	patios ratios
Nouns ending [consonant] y	story penny	change the y to an i and add es	stories pennies
Nouns ending [vowel] y	storey () donkey	add s	storeys donkeys
Mass nouns	glass rice	some nouns do not have a plural form	glass rice
Nouns ending f or fe	dwarf knife	ves and/or s (There are no rules - you have to know.)	dwarfs knives
Exceptions	goose louse	some nouns undergo a vowel or letters change	geese lice
More exceptions	salmon sheep	some nouns do not change at all	salmon sheep

Why Is There Confusion over the Plural of Glass?

Confusion arises because the plural is depends on the meaning of glass.

When talking about the material, glass is a mass noun. A mass noun is a noun without a plural form. They refer to items that can't be counted (e.g., music, milk, chalk).

When refering to the drinking container, the plural is glasses.

Of note, glasses is also another word for spectacles.

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