Plural of Basis

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The Quick Answer
The plural of basis is bases.

The Plural of Basis

The plural of basis is bases.
  • What are the bases of promotion?
  • Many countries are united in their belief in freedom, democracy, and human rights. However, these same beliefs are the bases of their division.
The noun basis has a Greek root, which is the derivation of the plural bases. There is no alternative English plural form. The noun basis 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 lamp
scythe		 add s lamps
scythes
Noun Ending s, sh, ch, x or z box
dress		 add es boxes
dresses
Nouns ending [consonant] o zero
tomato		 add either s or es
(There are no rules for this - you have to know.)		 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
Nouns ending is basis
thesis 		change the is to es bases
theses
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 fungus
medium 		some nouns adopt foreign rulings fungi
media

Why Is There Confusion over the Plural of basis?

bases is the only way to make the noun basis plural.

Confusion arises because some mistakenly believe that all nouns ending in s should form a plural that adds es to the end of the word. When a noun ends with is, you need to replace the is with an es to form the plural. This is because its plural form derives from Greek.

Of note, the plural bases is also the plural form of the noun base.
Another Interactive Exercise
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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