Skip to content

Plural of Index: Understanding the Correct Usage in American English

plural of index

In American English, the plural of “index” can be both “indexes” and “indices.” The usage of these plurals depends on the context in which they are used. While “indices” is commonly used in mathematical, scientific, and statistical contexts, “indexes” is typically used when referring to written documents like bibliographical or citation listings. However, it’s essential to note that both forms are widely accepted, and there is no strict rule on which one to use. The preference may vary depending on the individual or the style guide being followed.

The Singular and Plural of Index

  • Singular: Index
  • Plural: Indexes/Indices

The plural of “index” can be written as either “indexes” or “indices.” The use of one form over the other often depends on the context and the stylistic preference of the writer. Indexes” is commonly used in general contexts, while “indices” is preferred in technical or academic settings, especially in mathematics and related fields.

index plural spelling

Understanding Index


An "index" is a noun that refers to an alphabetical list of names, subjects, etc., with references to the places where they occur, typically found at the end of a book. It can also denote an indicator, sign, or measure of something.

Usage of Index

In usage, “index” varies depending on the field. In publishing, it refers to a list at the end of a book showing where particular subjects are discussed. In finance, an index represents a statistical measure of change in a securities market. In computer science, an index is a data structure used to quickly locate and access the data in a database.

Use of Index in Sentences

  1. Academic Context: “The professor emphasized that the index at the end of the textbook was crucial for quick referencing.”
  2. Technology: “To improve database performance, we added an index to the user ID column.”
  3. Finance: “The stock market reported a significant rise in the technology index last quarter.”
  4. General Use: “I checked the index of the cookbook to find a recipe for apple pie.
  5. Mathematics: “In differential calculus, the term ‘index’ denotes the exponent of a variable.”

Common Mistakes and Confusions

  • Indexes vs Indices: A common mistake is the interchangeable use of “indexes” and “indices.” While both are correct, “indices” is preferred in more technical or academic contexts.
  • Index vs Indexes/Indices: Confusion arises when deciding whether to use the singular or plural form. If referring to a single list or indicator, use “index”; for multiple, use “indexes” or “indices.”

Commonly Asked Questions

  1. Is “indices” only used in mathematical contexts?
    While “indices” is prevalent in mathematics, it’s also used in other technical or academic areas.
  2. Can “indexes” and “indices” be used interchangeably?
    Yes, but consider the context for appropriateness.
  3. How do I know which plural form to use?
    It often depends on the field of discussion and the stylistic preference of the writer or institution.
pluralization of index


Understanding the plural form of “index” as either “indexes” or “indices” is crucial for accurate and context-appropriate communication. This distinction not only enhances linguistic precision but also aids in clearer expression across various disciplines. Whether you are indexing a book, discussing stock indices, or referring to database indexes, recognizing the correct usage plays a key role in effective communication.


What is the correct plural form of “index”?

The correct plural forms of “index” in American English are both “indexes” and “indices.” The choice between the two depends on the context and individual preference.

When should I use “indexes” as the plural form?

“Indexes” is typically used when referring to written documents, such as bibliographical or citation listings.

In what contexts is “indices” preferred as the plural form?

Indices” is commonly used in mathematical, scientific, and statistical contexts.

Are both “indexes” and “indices” considered correct?

Yes, both “indexes” and “indices” are widely accepted and used as the plural forms of “index” in American English.

Which form of the plural is more commonly used in American English?

According to data from Google’s Ngram Viewer, “indices” has historically been more prevalent. However, “indexes” has gained popularity over the years and is now commonly used.

Is there a grammatical preference for “indexes” or “indices”?

There is no definitive rule on which form to use. Some argue that “indices” may sound more formal or technical, while “indexes” is often preferred in informal writing or non-technical contexts.

Should I use “indexes” or “indices” for consistency in my writing?

It is recommended to choose one form and use it consistently throughout a document or piece of writing for consistency.

What should I consider when deciding which form to use?

Consider the intended audience, the nature of the content, and any relevant style guides when deciding between “indexes” and “indices.”

Can I use either “indexes” or “indices” interchangeably?

Yes, both forms are considered correct and widely used. The preference may vary based on context and personal style.

What is the goal when deciding between “indexes” and “indices”?

The goal is effective communication. Using either “indexes” or “indices” accurately conveys the plural of “index.”

Jessica Smith

Jessica Smith

Jessica Smith, writer at, blends creativity with insight, exploring technology, culture, and psychology. With a background in English Literature, she crafts engaging stories inspired by nature and urban life. Outside writing, she enjoys exploring and continuous learning.View Author posts

Leave a Reply

Your email address will not be published. Required fields are marked *

Share this post on social!