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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.