Plural of index
The Quick Answer
The plural of "index" (mathematical) is "indices." The plural of "index" (directory or catalogue) is "indexes."The Plural of Index
In the world of mathematics, the plural of "index" is "indices." It has a Latin root, which is the derivation of the plural "indices."When used to refer to a directory, the noun "index," follows the standard English way of marking the plural and uses -es. The plural is "indexes."
- Indices are a useful way of more simply expressing large numbers. (In mathematics, the plural of index is indices.)
- The NASDAQ Index Directory provides a list of indexes. (The plural of index (a directory) is indexes.)
Are You Good at Plurals?
Here's a quick test.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 | index dress |
add es | indexes 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 | index diagnosis |
change the "is" to "es" | indices diagnoses |
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 Index?
Confusion arises because the plural of "index" change depending on the meaning of the word.If "index" is used in a mathematical context, the plural is "indices," which has a Latin root.
When used to refer to a directory, the plural of "index" is "indexes," which adheres to the standard rules for forming the plurals of nouns in English.
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