I still remember the first time I used the word “unfeasible” in an important work report. I had spent hours preparing the document and felt confident about every sentence. Then a colleague reviewed it and asked, “Why did you use unfeasible instead of infeasible?” That simple question stopped me in my tracks.
Honestly, I thought both words meant exactly the same thing. The more I looked into it, the more confused I became. Some dictionaries listed them as synonyms. Some style guides preferred one over the other. And when I searched online, I found writers, students, and professionals asking the same question: Should I use infeasible or unfeasible?
If you’ve ever hesitated before using these words, you’re definitely not alone. The confusion happens because both terms describe something that cannot realistically be done or achieved. They look similar, sound similar, and often appear in the same contexts. The good news is that the difference is much simpler than it seems.
In this guide, I’ll explain the meaning, history, usage, and practical differences between infeasible and unfeasible in simple English. By the end, you’ll know exactly which word to choose and when to use it confidently.
⚡Infeasible or Unfeasible – Quick Answer
Both infeasible and unfeasible mean not possible, impractical, or impossible to carry out.
However, infeasible is much more common in modern English, especially in business, academic, technical, and professional writing.
Quick Examples
- ✅ The project was infeasible because of budget limitations.
- ✅ Building the bridge became unfeasible after costs increased.
- ✅ Most formal documents prefer infeasible.
Simple Rule
Formal writing = Infeasible
Less common alternative = Unfeasible
🤔 Why Do People Confuse Infeasible or Unfeasible?
The confusion is understandable because both words mean nearly the same thing.
Several factors contribute to the mix-up.
1. They Share the Same Root Word
Both words come from feasible, which means possible or practical.
Adding the prefixes in- and un- creates a negative meaning.
2. Both Appear in Dictionaries
Many dictionaries define them similarly, making it difficult to identify a clear distinction.
3. They Sound Equally Correct
Unlike obvious mistakes, both words are grammatically valid.
That’s why writers often wonder which sounds more professional.
4. Style Guides Favor One Version
Many professional editors prefer infeasible, which leads some people to think unfeasible is wrong.
It isn’t wrong it is simply less common.
5. Context Matters
Technical and business writing heavily favor infeasible, while unfeasible occasionally appears in general writing.
📜 The Origin of Infeasible and Unfeasible
Understanding the history makes the difference easier to remember.
The Origin of Feasible
The word feasible comes from the French word faisable, meaning “capable of being done.”
It entered English during the 15th century.
The Origin of Infeasible
The prefix in- is commonly used in English to create opposites.
Examples include:
- Accurate → Inaccurate
- Complete → Incomplete
- Visible → Invisible
Following this pattern:
Feasible → Infeasible
The Origin of Unfeasible
The prefix un- also creates opposites.
Examples include:
- Happy → Unhappy
- Fair → Unfair
- Known → Unknown
This created:
Feasible → Unfeasible
Over time, however, infeasible became the dominant form in professional writing.
🌍 British vs American English
Unlike words such as color and colour, there is no major spelling difference between British and American English.
Both countries recognize both words.
| Feature | American English 🇺🇸 | British English 🇬🇧 |
| Infeasible | Common | Common |
| Unfeasible | Less Common | Less Common |
| Meaning | Same | Same |
| Formal Usage | Preferred | Preferred |
| Professional Writing | Frequent | Frequent |
Conclusion
Both forms are accepted internationally, but infeasible is generally preferred in both American and British English.
🎯 Which One Should You Use?
The safest choice is usually infeasible.
Use Infeasible When:
- Writing reports
- Academic papers
- Business documents
- Research studies
- Technical content
Examples:
✅ The proposed solution was infeasible.
✅ The timeline proved infeasible.
Use Unfeasible When:
- Writing casually
- Creating creative content
- Following house style preferences
Examples:
✅ The plan became unfeasible after funding was removed.
For Bloggers
Use infeasible because it sounds more professional and aligns with modern usage patterns.
For Freelancers
Clients often expect standard business English, making infeasible the safer option.
SEO Perspective
Searches for infeasible significantly outnumber searches for unfeasible, making it the stronger keyword in most cases.
❌ Common Mistakes (Avoid These!)
Mistake #1: Thinking Unfeasible Is Wrong
❌ Wrong:
“Unfeasible isn’t a real word.”
✅ Correct:
Unfeasible is a valid English word.
Mistake #2: Using Both in the Same Document
❌ Wrong:
“The plan is infeasible. The budget is unfeasible.”
✅ Correct:
Use one term consistently.
Mistake #3: Assuming They Have Different Meanings
❌ Wrong:
“They mean completely different things.”
✅ Correct:
They are nearly identical in meaning.
Mistake #4: Choosing Unfeasible in Formal Reports
❌ Wrong:
Using unfeasible in highly technical documents.
✅ Correct:
Most professionals prefer infeasible.
Mistake #5: Overthinking the Choice
❌ Wrong:
Spending excessive time deciding.
✅ Correct:
Simply choose infeasible for most situations.
📝 Real Life Examples
Emails
“The proposed deadline appears infeasible.”
“The current schedule is unfeasible due to staffing shortages.”
Social Media
“This challenge seems completely infeasible!”
“The goal became unfeasible after the rule changes.”
News Writing
“Officials described the proposal as economically infeasible.”
“Experts called the plan unfeasible under current conditions.”
Formal Writing
“The study concluded that implementation was infeasible.”
“The strategy became unfeasible because of resource constraints.”
📊 Quick Comparison Table
| Feature | Infeasible | Unfeasible |
| Meaning | Not practical or possible | Not practical or possible |
| Correct English | Yes | Yes |
| Formal Usage | Preferred | Less Common |
| Business Writing | Common | Rare |
| Academic Writing | Common | Rare |
| Casual Writing | Yes | Yes |
| American English | Preferred | Accepted |
| British English | Preferred | Accepted |
FAQs❓
1. Is infeasible the same as unfeasible?
Yes. Both generally mean impossible or impractical to accomplish.
2. Which is more common, infeasible or unfeasible?
Infeasible is significantly more common.
3. Is unfeasible grammatically correct?
Yes. It is a valid English word.
4. Which word sounds more professional?
Most professionals prefer infeasible.
5. Do British and American English use different versions?
No. Both varieties recognize both words.
6. Should students use infeasible or unfeasible?
Infeasible is usually the safer academic choice.
7. Is unfeasible outdated?
Not entirely, but it is much less common today.
8. Can I use either word in everyday conversation?
Yes. Most people will understand both.
Conclusion 🎯
The debate over infeasible or unfeasible is much simpler than it first appears.
Both words are legitimate English terms that describe something impractical, impossible, or difficult to achieve. Their meanings are nearly identical, which explains why so many writers struggle to choose between them.
However, modern English has clearly developed a preference.
In business reports, academic papers, technical writing, professional emails, and formal communication, infeasible is usually the better option. It appears more frequently, sounds more natural to many readers, and aligns with common style guide recommendations.
That doesn’t mean unfeasible is wrong. It remains a valid word and still appears in books, articles, and conversations. It’s simply less common.
If you’re ever unsure, remember this simple tip:
Infeasible = Preferred professional choice
Unfeasible = Correct but less common alternative
Follow that rule, and you’ll never have to second-guess your word choice again.
I’m Franz Kafka, an author at GrammarGuides.com, where I simplify English grammar for readers. As a grammar expert, I guide you through tricky rules and common mistakes.
