Plural of Glass

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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)

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The Standard Rules for Forming the Plurals

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.
Another Interactive Exercise
Here are three randomly selected questions from another exercise on plurals, which can be edited, printed to create an exercise worksheet, or sent via email to friends or students.

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See Also

Unusual pluralsPlural forming table Quirks with forming plurals Forming the plurals of abbreviations Forming the plurals of compound nouns