Plural of Formula

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The Quick Answer
The plural of formula is formulas or formulae.

The Plural of Formula

The plural of formula is formulas or formulae.
  • Formulas are applied to provide a mathematical solution for real world problems.
  • Formulae are used to express relationships between various quantities.
The noun formula has a Latin root, which is the derivation of the plural formulae. Through common usage, formulas (which adheres to the standard rules for forming plurals) is also now acceptable.

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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 formula
scythe		 add s formulas
scythes
Noun Ending s, sh, ch, x or z box
dress		 add es boxes
dresses
Nouns ending [consonant] o hero
zero
tomato		 add either s or es
(There are no rules for this - you have to know.)		 heroes
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 donkey
chimney 		add s donkeys
chimneys
Nouns ending f or fe dwarf
hoof 		ves and/or s
(There are no rules - you have to know.)		 dwarfs
hooves or hoofs
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
Foreign rulings formula
medium 		some nouns adopt foreign rulings formulae
media

Why Is There Confusion over the Plural of Formula?

Confusion arises over the plural of formula because its original plural form (formulae) derives from Latin, and native English speakers are drawn to formulas, which adheres to the standard ruling for forming plurals.

Both formulae and formulas are acceptable, but formulas is the more common plural and the safest option. (See the evidence in Google's Ngram Viewer.)
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