Plural of Furnace

The Quick Answer

The plural of "furnace" is "furnaces."

The Plural of Furnace

The plural of "furnace" is "furnaces."
  • The most common fuel source for modern furnaces in the United States is natural gas correct tick
  • Today's furnaces are much more energy-efficient than those from the past. correct tick
The noun "furnace" adheres to the standard rules for forming the plurals of nouns in English (shown in the table below).

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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 furnace
scythe
add s furnaces
scythes
Noun Ending s, sh, ch, x or z bus
dress
add es buses
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 (small British flag)
donkey
add s storeys
donkeys
Nouns ending f or fe dwarf
knife
ves and/or s
(There are no rules - you have to know.)
dwarfs
knives
Exceptions man
louse
some nouns undergo a vowel or letters change men
lice
More exceptions salmon
sheep
some nouns do not change at all salmon
sheep
Read more about English spelling rules.

Why Is There Confusion over the Plural of Furnace?

There is confusion because inexperienced writers often feel compelled to add an apostrophe when a noun ends with a vowel (e.g., piano, tomato, emu). Adding 's is never an option when forming the plural of a noun.
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This page was written by Craig Shrives.