What Is the Plural of Formula?
The word formula has two correct plural forms: formulas and formulae. Both are widely accepted, but they are used in different contexts. Formulas is the standard plural in everyday English, while formulae is the traditional Latin plural, often found in scientific, mathematical, and formal writing. Your choice depends on your audience and the tone you want to set.
Quick Answer
- Formulas – Common in general English, business, and informal writing.
- Formulae – Preferred in academic, scientific, and technical contexts.
- Both are grammatically correct. Use formulas for clarity and formulae for a formal or traditional tone.
Understanding the Two Plurals
The word formula comes from Latin, where its plural was formulae. Over time, English speakers began applying the regular English plural rule (adding -s or -es), creating formulas. Today, both forms exist, and neither is wrong. However, the choice can signal the level of formality or the field you are writing in.
When to Use “Formulas”
Formulas is the safer, more modern choice. It is the dominant form in everyday writing, including emails, business reports, news articles, and casual conversation. If you are unsure which to use, formulas is usually the best option.
- Context: General writing, business, informal emails, blog posts, and conversation.
- Tone: Neutral, clear, and accessible.
- Example: “The spreadsheet contains several complex formulas for calculating profit margins.”
When to Use “Formulae”
Formulae is the Latin plural and carries a more formal or academic tone. It is common in mathematics, physics, chemistry, and other sciences. You will also see it in legal or technical documents where precision and tradition are valued. However, using formulae in a casual email can sound stiff or pretentious.
- Context: Scientific papers, textbooks, academic journals, formal reports.
- Tone: Formal, traditional, precise.
- Example: “The chemist derived several new formulae during the experiment.”
Comparison Table: Formulas vs. Formulae
| Aspect | Formulas | Formulae |
|---|---|---|
| Origin | English plural rule (-s) | Latin plural rule (-ae) |
| Common usage | Everyday English, business, media | Academic, scientific, technical |
| Tone | Neutral, modern, clear | Formal, traditional, precise |
| Audience | General readers, colleagues, clients | Researchers, professors, specialists |
| Example sentence | “We updated the formulas in the report.” | “The formulae are listed in the appendix.” |
| Frequency | More common in modern English | Less common, but standard in science |
Natural Examples
Seeing both forms in real contexts helps you decide which to use. Here are examples from different situations.
Everyday Conversation
- “I can’t remember all the formulas for the test tomorrow.”
- “She showed me the formulas she used to budget her trip.”
Business Email
- “Please double-check the formulas in the attached spreadsheet before the meeting.”
- “Our team developed new formulas to predict customer demand.”
Academic Writing
- “The researcher presented several formulae for calculating energy efficiency.”
- “These formulae have been standard in physics for decades.”
Scientific Report
- “The appendix contains all the formulae used in the study.”
- “We compared our results with the formulae from previous experiments.”
Common Mistakes
Even advanced English learners sometimes make errors with these plurals. Here are the most frequent mistakes and how to avoid them.
Mistake 1: Using “Formulae” in Casual Writing
Using formulae in an email to a colleague or in a blog post can sound overly formal. Stick with formulas for everyday communication.
Incorrect: “I need to check the formulae in your report before I send it to the client.” (Too formal for internal communication)
Correct: “I need to check the formulas in your report before I send it to the client.”
Mistake 2: Mixing Both Forms in One Document
Choose one form and use it consistently throughout your document. Switching between formulas and formulae can confuse readers.
Incorrect: “The formulas are correct, but the formulae in the appendix need updating.”
Correct: “The formulas are correct, but the formulas in the appendix need updating.”
Mistake 3: Using “Formulas” in Formal Scientific Papers
In some academic journals, formulae is still the expected form. Check the style guide of the publication you are writing for.
Incorrect (in a physics journal): “The formulas derived by Newton are still relevant.”
Correct (in the same journal): “The formulae derived by Newton are still relevant.”
Better Alternatives and When to Use Them
Sometimes, you can avoid the choice altogether by rephrasing. This is especially useful if you are unsure which plural fits best.
- Instead of: “We need to review the formulas/formulae.”
Say: “We need to review the calculations.” - Instead of: “The formulas/formulae are complex.”
Say: “The mathematical expressions are complex.” - Instead of: “She wrote down the formulas/formulae.”
Say: “She wrote down the equations.”
Using synonyms like calculations, equations, or expressions can make your writing clearer and avoid the plural dilemma entirely.
Mini Practice: Test Your Knowledge
Choose the correct plural for each sentence. Answers are below.
- The engineer checked all the __________ before running the simulation.
a) formulas
b) formulae
c) both are correct - In her chemistry thesis, she listed twenty different __________.
a) formulas
b) formulae
c) both are correct - Please update the __________ in the budget spreadsheet.
a) formulas
b) formulae
c) both are correct - The textbook includes a chapter on advanced mathematical __________.
a) formulas
b) formulae
c) both are correct
Answers
- c) both are correct – In a general context, either works. Formulas is more common in everyday speech.
- b) formulae – A chemistry thesis is a formal academic context where formulae is preferred.
- a) formulas – A budget spreadsheet is a business context; formulas is the natural choice.
- c) both are correct – In a textbook, either is acceptable, though formulae may feel more academic.
Frequently Asked Questions
1. Is “formula” ever used as a plural?
No. Formula is always singular. The plural is either formulas or formulae. Using formula for more than one is incorrect.
2. Which plural is more common in American English?
Formulas is far more common in American English, even in academic writing. Formulae is used but is less frequent and often seen as old-fashioned.
3. Which plural is more common in British English?
Both are used, but formulae appears more often in British academic and scientific writing than in American English. In everyday British English, formulas is still the standard.
4. Can I use “formulae” in an email to my boss?
It depends on your workplace culture. If your boss is a scientist or works in a formal academic environment, formulae may be fine. In most business settings, formulas is safer and sounds more natural.
Final Tip
When in doubt, use formulas. It is correct in almost every situation and will never sound out of place. Reserve formulae for formal scientific or academic writing where tradition and precision matter. By understanding the context and your audience, you can confidently choose the right plural every time.
For more help with plural forms, explore our guides on Common Plural Forms or check our FAQ for quick answers. If you have questions about other tricky plurals, visit our contact page to let us know.
