Determining the correct plural form of the word appendix is a fascinating journey into the history of the English language and its relationship with Latin. In English, we often encounter nouns that follow standard pluralization rules, but others retain their classical roots, leading to variations such as appendices, appendixes, indices, vortices, and matrices. Understanding these distinctions is essential for anyone working in academic, medical, or technical fields where precision in terminology is paramount. This guide will explore the etymological origins of the word, the specific contexts in which each plural form is preferred, and the grammatical rules that govern these shifts in spelling and usage.
Whether you are a student writing a research paper, a medical professional documenting patient charts, or a writer crafting a book, knowing when to use the Latin-derived or the Anglicized plural can significantly impact the tone and clarity of your work. While both forms are technically acceptable in many modern dictionaries, they carry different connotations and are typically favored by different style guides. By mastering these nuances, you can ensure that your writing remains professional and accurate across various disciplines. This article provides a deep dive into the structural breakdown, usage rules, and practical applications of this common yet often confusing grammatical challenge.
Table of Contents
- Definition and Etymology of Appendix
- Structural Breakdown: Why Two Plurals?
- Latin vs. English Pluralization Patterns
- The Anatomical Context: Appendixes in Medicine
- The Literary Context: Appendices in Publications
- Extensive Comparative Tables of Plural Nouns
- Comprehensive Usage Rules and Style Guides
- Common Mistakes and How to Avoid Them
- Advanced Topics: The -ix and -ex Suffixes
- Practice Exercises and Knowledge Checks
- Frequently Asked Questions (FAQ)
- Conclusion and Final Summary
Definition and Etymology of Appendix
The word appendix functions as a noun in the English language, referring to something that is joined or attached to a larger or more important entity. In a general sense, it represents an addition or a supplement that provides further information or completes a whole. The term is most commonly used in two distinct fields: literature (referring to supplementary material at the end of a book) and anatomy (referring to the small, tube-shaped sac attached to the large intestine).
To understand the plural forms, we must look at the word’s Latin origins. It stems from the Latin appendere, which means “to hang upon” or “to weigh out.” The root pendere (to hang) is also found in English words like pendant, pendulum, and depend. In Latin, the word followed the third declension, where nouns ending in -ix or -ex typically changed to -ices in the plural. This historical legacy is why the form appendices remains so prevalent in formal English today.
In modern usage, the classification of the word depends on its functional context. As a concrete noun in anatomy, it refers to a physical organ. As an abstract or technical noun in publishing, it refers to a section of text. Because English is a living language that tends to simplify complex foreign rules over time, the Anglicized version appendixes emerged to follow the standard -es pluralization rule applied to words ending in x, similar to boxes or taxes.
Structural Breakdown: Why Two Plurals?
The existence of two plural forms for appendix is a result of a linguistic process known as “regularization.” This occurs when a word borrowed from another language gradually adopts the standard grammatical rules of the host language. In English, the standard rule for making a noun plural is adding -s or -es. However, for words with deep roots in Latin or Greek, the original “foreign” plural often persists, especially in academic and scientific circles.
The Latin pluralization rule involves changing the -ix ending to -ices. This is a phonetic shift where the “ks” sound of the x is replaced by a “s” or “ts” sound followed by the plural marker. This results in appendices (pronounced uh-PEN-duh-seez). On the other hand, the English rule simply appends -es to the singular form, resulting in appendixes (pronounced uh-PEN-dix-iz). Both are considered grammatically correct, but they are not always interchangeable in terms of style.
This structural duality is common among many English words of Latin origin. Words like index (indices/indexes), matrix (matrices/matrixes), and vertex (vertices/vertexes) all exhibit this same behavior. The choice between the two often signals the writer’s intended level of formality. The Latinate form is perceived as more sophisticated or traditional, while the Anglicized form is seen as more modern and accessible.
Latin vs. English Pluralization Patterns
When we examine the patterns of pluralization, we see that English often struggles to reconcile its Germanic roots with its heavy Latin influence. For most words ending in -x, English speakers instinctively add -es. For example, the plural of fox is foxes, and the plural of tax is taxes. This provides a consistent framework for the language. However, the scientific revolution and the Renaissance brought a wave of Latin terms into English that resisted this simplification for centuries.
In the case of appendix, the Latin pattern -ix to -ices is part of a larger group of nouns. This category includes technical terms used in mathematics, biology, and law. The retention of the Latin plural often serves to maintain a connection to the global scientific community, where Latin was once the lingua franca. If you are writing for a peer-reviewed journal, the Latin pattern is almost always the expected choice because it adheres to the historical conventions of the field.
Conversely, the English pattern is gaining ground in general communication. News reports, blog posts, and casual correspondence are more likely to use appendixes. This shift reflects the natural evolution of English toward a more uniform system. It is important to note that while appendixes is becoming more common, it has not yet fully displaced appendices in the way that formulas has largely replaced formulae in everyday speech. The choice remains a matter of register and audience.
The Anatomical Context: Appendixes in Medicine
In the field of medicine and biology, the word appendix usually refers to the appendix vermiformis. Interestingly, this is the one area where the Anglicized plural, appendixes, is frequently accepted and even preferred by some modern medical dictionaries. When doctors discuss multiple patients who have had their appendixes removed, or when discussing the anatomical variations of the organ across different species, appendixes is a common term.
However, many traditional medical texts still stick to appendices. This creates a bit of a divide within the healthcare community. The key is consistency. If a medical journal uses appendices in its primary research articles, a contributor should follow suit. If a hospital’s patient education brochure uses appendixes to make the information more readable for the general public, that is also a valid choice. The anatomical context is unique because it deals with a physical object rather than a conceptual one.
When describing the inflammation of the appendix, we use the term appendicitis. Because this is a singular condition, the pluralization of the organ itself rarely comes up in the name of the disease. However, in comparative anatomy studies—such as comparing the digestive systems of various mammals—the plural form is essential. In these high-level scientific contexts, you will find a strong preference for the classical appendices to maintain a formal, objective tone.
The Literary Context: Appendices in Publications
In the world of publishing and academia, an appendix is a section at the end of a document that contains supplementary information, such as raw data, maps, interview transcripts, or detailed charts. Because these documents are often formal in nature, the Latin plural appendices is the overwhelming favorite. Style guides like the Chicago Manual of Style (CMS), the American Psychological Association (APA), and the Modern Language Association (MLA) generally lean toward appendices when referring to these bibliographic elements.
Using appendices in a thesis or a book suggests a level of scholarly rigor. It signals to the reader that the author is familiar with the conventions of formal writing. For example, a textbook might state, “For further details on the statistical methods used, please refer to Appendices A and B.” This usage feels more natural to the academic ear than “Appendixes A and B.” The literary context relies heavily on tradition and the established norms of the publishing industry.
That being said, if you are writing a less formal report or a corporate manual, appendixes is perfectly acceptable. The goal in these documents is often clarity and ease of reading. If your audience is not composed of academics, the simpler English plural might be less distracting. Always check your specific organization’s style guide to see if they have a mandated preference for one form over the other.
Extensive Comparative Tables of Plural Nouns
To help visualize the patterns of pluralization for words like appendix, the following tables provide numerous examples of nouns that follow similar rules. These tables compare the Latinate plural with the Anglicized plural and provide context for their usage.
Table 1: Nouns Ending in -ix and -ex
This table demonstrates the shift from the singular -ix/-ex ending to the plural -ices or -es. It highlights how common this pattern is in the English language.
| Singular Form | Latinate Plural (Classical) | Anglicized Plural (Modern) | Primary Context |
|---|---|---|---|
| Appendix | Appendices | Appendixes | Books/Anatomy |
| Index | Indices | Indexes | Math/Books |
| Matrix | Matrices | Matrixes | Math/Science |
| Vertex | Vertices | Vertexes | Geometry |
| Vortex | Vortices | Vortexes | Physics |
| Cortex | Cortices | Cortexes | Biology |
| Helix | Helices | Helixes | Science/Engineering |
| Calyx | Calyces | Calyxes | Botany |
| Codex | Codices | Codexes | History/Manuscripts |
| Apex | Apices | Apexes | General/Scientific |
| Cicatrix | Cicatrices | Cicatrixes | Medical (Scars) |
| Directrix | Directrices | Directrixes | Mathematics |
| Radix | Radices | Radixes | Math/Linguistics |
| Silex | Silices | Silexes | Geology |
| Varix | Varices | Varixes | Medical (Veins) |
| Thorax | Thoraces | Thoraxes | Anatomy/Insects |
| Cervix | Cervices | Cervixes | Anatomy |
| Larynx | Larynges | Larynxes | Anatomy |
| Pharynx | Pharynges | Pharynxes | Anatomy |
| Meninx | Meninges | Meninxes | Anatomy |
The table above shows that while many words have both forms, some (like meninges) almost exclusively use the Latinate plural in professional settings. This illustrates the importance of context when choosing the correct form.
Table 2: Common Latin Plurals in Academic Writing
Academic writing often preserves Latin plurals for a wide variety of words. This table shows appendix alongside other common academic terms to show the consistency of the -i, -a, and -es endings.
| Singular Form | Plural Form | Example Sentence |
|---|---|---|
| Appendix | Appendices | The raw data is located in the appendices. |
| Criterion | Criteria | The selection criteria were very strict. |
| Phenomenon | Phenomena | Natural phenomena are difficult to predict. |
| Stimulus | Stimuli | The plants responded to various stimuli. |
| Alumnus | Alumni | The alumni met for a reunion. |
| Curriculum | Curricula | The school offers several different curricula. |
| Medium | Media | The media play a role in public opinion. |
| Bacterium | Bacteria | These bacteria are resistant to antibiotics. |
| Nucleus | Nuclei | The nuclei of these cells are enlarged. |
| Syllabus | Syllabi | Please review the course syllabi. |
| Thesis | Theses | The students submitted their theses in May. |
| Analysis | Analyses | The analyses conducted were comprehensive. |
| Focus | Foci | The research has two primary foci. |
| Radius | Radii | The radii of the circles were equal. |
| Cactus | Cacti | The desert is full of various cacti. |
| Fungus | Fungi | Some fungi are edible, while others are toxic. |
| Larva | Larvae | The larvae transform into butterflies. |
| Alga | Algae | The pond was covered in green algae. |
| Nebula | Nebulae | The telescope captured images of distant nebulae. |
| Stratum | Strata | Different social strata were represented. |
As seen in the table, appendices fits perfectly into the pattern of formal academic language. Using the Latinate plural helps maintain a consistent tone when other Latin-derived plurals are used in the same text.
Table 3: Pluralization Frequency in Different Disciplines
This table provides a snapshot of which plural form is more likely to be encountered in specific professional fields.
| Field of Study | Preferred Plural | Reasoning for Preference |
|---|---|---|
| Medical Surgery | Appendixes | Modern clinical practice favors English standardization. |
| Scientific Research | Appendices | High formality and adherence to Latin roots. |
| Legal Documents | Appendices | Traditional legal language relies on Latin precision. |
| Casual Blogging | Appendixes | Accessibility and conversational tone. |
| Mathematics | Appendices | Consistency with other terms like indices. |
| Technical Writing | Appendixes | Focus on clear, simplified communication. |
| Historical Research | Appendices | Respect for classical linguistic traditions. |
| General Fiction | Appendixes | Follows standard English rules for readability. |
| Publishing (Manuals) | Appendices | Standard industry convention for back matter. |
| Government Reports | Appendices | Formal bureaucratic style. |
Comprehensive Usage Rules and Style Guides
Navigating the choice between appendices and appendixes requires an understanding of the rules set forth by major style guides. These guides act as the “law” for specific types of writing, and following them ensures that your work meets the professional standards of your industry. While there is no single “correct” answer for all of English, there is usually a correct answer for your specific context.
1. The Rule of Consistency: The most important rule in any writing is consistency. If you choose to use appendices on page 5, you must not use appendixes on page 20. Mixing the two forms within the same document is considered a sign of poor editing and can confuse the reader. Before you begin writing, decide which form fits your tone and stick with it throughout the entire project.
2. The Rule of Formality: As a general guideline, the more formal the document, the more likely you are to use appendices. This includes academic dissertations, peer-reviewed journals, and legal briefs. Conversely, if you are writing a user manual for a consumer product or a casual newsletter, appendixes is often the better choice because it feels less “stuffy” and more aligned with everyday speech.
3. Style Guide Specifics:
- APA Style: Generally prefers appendices when referring to the sections at the end of a research paper.
- Chicago Manual of Style (CMS): Lists appendices as the primary plural for literary supplements.
- Associated Press (AP) Style: AP style often favors the simpler, Anglicized versions of words. In many cases, it accepts appendixes, although appendices is still common in specific contexts.
- Scientific Style and Format (CSE): Strongly favors appendices to maintain international scientific standards.
4. Geographical Variations: There is also a slight difference between British English and American English. British English tends to be more conservative and often retains the Latin appendices more frequently than American English. In the United States, the push toward “simplified” English has made appendixes more common in corporate and journalistic settings than it is in the UK.
Common Mistakes and How to Avoid Them
Even though both plural forms are technically correct, there are several common mistakes that writers make when dealing with these words. Avoiding these pitfalls will help you maintain a high level of professional credibility.
Mistake 1: Misspelling the Latin Plural. Many writers try to use the Latin form but misspell it as appendixes or appendicees. Remember that the -ix changes to -ices. If you want the formal version, it must be appendices. A helpful trick is to think of the word ice—the plural ends in -ices.
Mistake 2: Using the Plural for the Singular. Sometimes a writer will refer to a single supplementary section as “the appendices.” This is incorrect. If you are only referring to one section, use appendix. For example: “See Appendix A.” Only use the plural when referring to two or more sections: “See Appendices A and B.”
Mistake 3: Inconsistency within a Series. In a list of multiple items, some writers might accidentally switch forms. For example: “The indices and appendixes are located at the back.” It is much better to say “The indices and appendices” or “The indexes and appendixes.” Keeping the “Latin-ness” or “English-ness” consistent across different words in the same sentence creates a better flow.
Mistake 4: Incorrect Pronunciation. While this is a writing guide, pronunciation often influences spelling. Some people mispronounce appendices as “uh-PEN-dix-eez.” The correct pronunciation is “uh-PEN-duh-seez.” Knowing the correct sound can help you remember the correct -ices spelling.
Advanced Topics: The -ix and -ex Suffixes
For advanced learners and linguistics enthusiasts, the study of -ix and -ex suffixes reveals a lot about how English absorbs foreign vocabulary. These suffixes are characteristic of Latin third-declension nouns. In Latin, the x was a shorthand for a c or g sound combined with an s. When these words were pluralized, the s changed, and the underlying c became visible, leading to the -ices ending.
This linguistic history explains why we see similar patterns in words like crux (cruces), lux (luces), and dux (duces), although most of these have been fully Anglicized in modern English. The fact that appendix, index, and matrix still retain their Latin plurals is a testament to their continued use in specialized fields that value historical continuity. In mathematics, for example, matrices is almost the only form used; matrixes sounds distinctly amateurish to a mathematician.
Another interesting aspect is the “gender” of these words in Latin. Most -ix nouns were feminine. While English has discarded grammatical gender for inanimate objects, the formal pluralization remains a “fossilized” remnant of that complex system. Understanding this helps advanced students appreciate that grammar is not just a set of arbitrary rules, but a reflection of thousands of years of human communication and cultural exchange.
Practice Exercises and Knowledge Checks
To master the use of appendix and its plurals, try the following exercises. These are designed to test your understanding of context, spelling, and style guide adherence.
Exercise 1: Choose the Correct Form
Select the most appropriate plural form based on the context provided in the sentence.
- In his formal doctoral dissertation, the student included three ________ (appendices / appendixes) containing his raw data.
- The surgeon noted that both ________ (appendices / appendixes) removed during the study showed signs of chronic inflammation.
- When you look at the back of the user manual, you will find several ________ (appendices / appendixes) with troubleshooting tips.
- The book’s ________ (appendices / appendixes) were organized alphabetically for easy reference.
- Modern medical textbooks often refer to the ________ (appendices / appendixes) of different primates to show evolutionary changes.
- Please ensure that the ________ (indices / indexes) and ________ (appendices / appendixes) are formatted consistently.
- The legal contract had four ________ (appendices / appendixes) attached to the main body of the agreement.
- In casual conversation, she mentioned that the ________ (appendices / appendixes) in the back of the book were too long.
- The mathematical paper explored the ________ (matrices / matrixes) found in the ________ (appendices / appendixes).
- Most style guides for academic writing recommend using ________ (appendices / appendixes).
Exercise 2: Identifying Style and Tone
Read the following sentences and decide if the tone is Formal/Academic or Informal/General. Then, identify if the plural choice matches that tone.
| Sentence | Tone | Is the Plural Appropriate? |
|---|---|---|
| “Check the appendixes in the IKEA manual for the parts list.” | Informal/General | Yes |
| “The researcher analyzed the appendices for statistical errors.” | Formal/Academic | Yes |
| “Yo, did you see the appendices in that comic book?” | Informal/General | No (too formal) |
| “The anatomical structures of the appendixes were photographed.” | Formal/Medical | Yes (modern medical style) |
| “The appendices of the treaty were signed by all parties.” | Formal/Legal | Yes |
Exercise 3: Answer Key and Explanations
| Question | Correct Answer | Explanation |
|---|---|---|
| Ex 1, Q1 | Appendices | Dissertations are formal academic documents. |
| Ex 1, Q2 | Appendixes | Medical context often accepts the Anglicized plural. |
| Ex 1, Q3 | Appendixes | User manuals are generally less formal. |
| Ex 1, Q7 | Appendices | Legal contracts require high formality. |
| Ex 1, Q9 | Matrices/Appendices | Mathematical papers use Latinate forms. |
Frequently Asked Questions (FAQ)
Q: Is “appendices” more correct than “appendixes”?
A: Neither is “more” correct in a vacuum; both are recognized by dictionaries. However, appendices is the standard for academic, scientific, and legal writing, while appendixes is common in medical and general contexts.
Q: How do I pronounce “appendices”?
A: It is pronounced uh-PEN-duh-seez. The second syllable is stressed, and the ending sounds like the word “sees.”
Q: Can I use “appendixes” in a college essay?
A: While your professor might not mark it as a “red ink” error, using appendices is safer in a college environment as it demonstrates a higher level of academic literacy.
Q: Why does the “x” change to a “c” in the plural?
A: This is due to the word’s Latin origin. In Latin, the root of the word ended in a “c” sound, which combined with the “s” plural marker to form an “x.” In the plural form appendices, the original “c” becomes visible again.
Q: Does this rule apply to the word “index” too?
A: Yes. Index can be pluralized as indices (formal/mathematical) or indexes (books/general). The pattern is identical to appendix.
Q: What if I am referring to the organ, not a book section?
A: In a medical context, appendixes is very common and widely accepted. However, if you are writing a formal biological research paper, appendices is still frequently used.
Q: Is there a plural for “appendicitis”?
A: No. Appendicitis is the name of a medical condition (inflammation), which is an uncountable noun. You would say “cases of appendicitis,” not “appendicitises.”
Q: Which form does Microsoft Word’s spellcheck prefer?
A: Most modern spellcheckers recognize both. However, they may flag appendixes in a document that it perceives as highly formal, or vice versa, depending on the software’s settings.
Conclusion and Final Summary
Mastering the plural of appendix is a small but significant step in becoming a more polished and professional writer. By recognizing that appendices is the preferred choice for academic and formal literary contexts, while appendixes is often suitable for medical and general use, you can tailor your language to your specific audience. The most important takeaway is to remain consistent within your own writing. Choose the form that matches the tone of your document and stick with it. Remember that grammar is a tool for clarity; whether you use the Latinate or the Anglicized form, your goal should always be to communicate your ideas as effectively as possible. Keep practicing with different types of nouns, and soon these classical plural patterns will become second nature to you.
