Unfeasible or Infeasible: Which Word Is Correct?

“Unfeasible or Infeasible: Both words are correct and mean something that is not practical or possible to achieve. Infeasible is more commonly used in technical and formal contexts, while unfeasible is less common”.

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Have you ever tried to describe a plan that seems too difficult, expensive, or impossible to complete? You might write that the plan is unfeasible. Someone else might use the word infeasible to describe the same situation. This can make you wonder if one spelling is correct and the other is wrong.

The good news is that both unfeasible and infeasible are correct English words. They have the same basic meaning: something cannot be done or achieved in a practical way. Neither word is a spelling mistake, and both appear in dictionaries. However, infeasible is often preferred in technical, academic, and professional writing, while unfeasible is also accepted in everyday English.

The choice usually depends on your writing style and the context. You do not need to learn two completely different meanings to use these words correctly.

In this guide, you will learn what each word means, how they compare, when to use them, and how to avoid common mistakes.

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Quick Answer: Unfeasible or Infeasible?

Both unfeasible and infeasible are correct spellings. They mean that something is not feasible, practical, or achievable.

• Unfeasible: Correct word meaning not feasible or difficult to achieve in practice.
• Infeasible: Correct word with the same basic meaning, often used in technical or formal contexts.
• Not feasible: A clear alternative that works in almost any context.

You can use either word to describe a plan that cannot realistically be completed. The two words are generally interchangeable, so you should not treat unfeasible as incorrect.

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What Does Unfeasible Mean?

Unfeasible is an adjective. It describes something that cannot reasonably be done or achieved under the available conditions.

A plan might be unfeasible because it costs too much, requires more time than is available, or depends on resources that cannot be obtained. The word focuses on if an idea can work in practice.

For example, a business may want to open ten new offices in one month. If it does not have enough money, workers, or equipment, the plan may be unfeasible.

The word does not always mean that something is impossible forever. A plan that is unfeasible today might become possible when circumstances change.

Examples of Unfeasible

• The project became unfeasible because the budget was too small.
• Building the road in two days would be unfeasible.
• The team rejected an unfeasible plan.
• The idea sounded exciting, but it was unfeasible with the available resources.

In each sentence, unfeasible describes a plan or action that cannot reasonably be achieved.

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What Does Infeasible Mean?

Infeasible is also an adjective. It means that something is not feasible or cannot be achieved in a practical way.

The word is common in technical reports, research, business planning, engineering, mathematics, and computer science. In these fields, people may use it when a task cannot meet certain requirements or limits.

For example, a computer program might need to find a solution that meets several rules. If no solution meets those rules, the task may be described as infeasible.

In everyday writing, infeasible can describe the same kinds of situations as unfeasible. It does not automatically mean that something is more impossible or more difficult.

Examples of Infeasible

• The plan was infeasible because the deadline was too short.
• The engineers found the design infeasible.
• The company decided that the proposal was financially infeasible.
• Completing every task in one hour would be infeasible.

These sentences show how infeasible can describe practical limits in work, planning, and technical situations.

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What Is the Difference Between Unfeasible and Infeasible?

The main difference is the prefix used to form each word. Unfeasible begins with un-, while infeasible begins with in-. Both prefixes can express a negative meaning in English.

Feature	Unfeasible	Infeasible
Correct spelling	Yes	Yes
Part of speech	Adjective	Adjective
Basic meaning	Not feasible	Not feasible
Common use	General and everyday writing	General, formal, and technical writing
Is it a misspelling?	No	No
Can it replace the other?	Usually, yes	Usually, yes

There is no strict rule that gives these words completely different meanings. In many sentences, you can replace one with the other without changing the main idea.

For clear writing, choose the word that fits the style of your document. If you are unsure, not feasible is a simple and natural alternative.

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Are Unfeasible and Infeasible Interchangeable?

Yes. In most situations, these words are interchangeable because both describe something that is not practical or cannot be achieved.

Consider the following sentences:

• The proposal is unfeasible because it costs too much.
• The proposal is infeasible because it costs too much.

Both sentences communicate the same idea. The high cost makes the proposal difficult or impossible to carry out under the current conditions.

However, a company, university, or technical publication may prefer one term for consistency. If an organization uses infeasible in its reports, following that style can make your writing more consistent.

The important point is that you should not assume the words have separate meanings just because their prefixes are different.

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When Should You Use Unfeasible?

Use unfeasible when you want to describe a plan, goal, action, or idea that cannot realistically be achieved. It works in everyday writing as well as in formal communication.

In Everyday English

You can use unfeasible when talking about personal plans or daily tasks.

For example:

• Visiting five cities in one afternoon is unfeasible.
• Buying a new house this month is unfeasible for me.
• Finishing the entire book tonight seems unfeasible.

These sentences describe plans that may not work because of time, money, or other practical limits.

In Business and Planning

The word can also describe business ideas and projects.

For example:

• The company considered the expansion plan unfeasible.
• Hiring fifty new workers this week would be unfeasible.
• The manager rejected the unfeasible schedule.

Here, the word explains why a plan may not work with the available resources.

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When Should You Use Infeasible?

Use infeasible when it suits the tone of your writing. It is especially common in technical and formal contexts, although it is not limited to them.

In Technical Writing

Technical writers may use infeasible to describe a solution that cannot satisfy a system’s requirements.

For example:

• The proposed design was technically infeasible.
• The software returned an infeasible solution.
• The engineers identified several infeasible options.

In these cases, the word fits a precise discussion of technical limits.

In Academic and Research Writing

Researchers may use infeasible when discussing a method, experiment, or proposal that cannot realistically be carried out.

For example:

• The study design was infeasible within the available budget.
• The researchers found the original method infeasible.
• Collecting all the required data in one day was infeasible.

The word is useful in academic writing because it can describe limits related to time, money, equipment, or research conditions.

Remember that unfeasible can also work in many of these sentences. The context does not make the other word incorrect.

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Is One Word More Common Than the Other?

Usage can change over time. Both words have a long history in English, and both remain in use.

English-language usage discussions report that unfeasible was more common earlier, while infeasible became more common around the 1970s. Modern usage can vary by subject, publication, and type of writing.

The important lesson is not to choose a word based on the belief that the other is wrong. Instead, consider your audience and the style of your document.

For a technical report, infeasible may sound more familiar to readers in that field. For a general audience, either unfeasible or not feasible can communicate the idea clearly.

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Is Unfeasible a Real Word?

Yes. Unfeasible is a real English word listed in dictionaries. It is not simply a typo or an invented alternative to infeasible.

Cambridge Dictionary lists unfeasible with the meaning “not feasible” and also points readers to infeasible. This confirms that both forms are accepted.

Some people prefer infeasible because it is common in formal or technical writing. That preference does not make unfeasible incorrect.

If you see unfeasible in a book, article, or professional document, you do not need to assume it is an error.

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Is Infeasible a Real Word?

Yes. Infeasible is a standard English adjective. It means that something cannot be achieved or carried out in a practical way.

It appears in general dictionaries and is used in areas such as engineering, economics, research, and computing.

For example, a project might be infeasible because its cost exceeds the available budget. A technical solution might be infeasible because it fails to meet required conditions.

Do not confuse infeasible with invisible or ineffective. These words have different meanings even though they begin with the same prefix.

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What Is the Difference Between Feasible and Infeasible?

Feasible means possible or practical to do. Infeasible means not feasible.

The two words express opposite ideas.

Word	Meaning	Example
Feasible	Practical or possible to achieve	The plan is feasible with our current budget.
Infeasible	Not practical or possible to achieve	The plan is infeasible with our current budget.
Unfeasible	Not practical or possible to achieve	The plan is unfeasible with our current budget.

The prefix changes the meaning from something that can be done to something that cannot reasonably be done.

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Common Mistakes to Avoid

When using these words, remember the following points:

1. Do not call unfeasible incorrect. It is an accepted English word.
2. Do not assume infeasible always means completely impossible. It often refers to practical limits.
3. Do not invent a strict difference between the two. Their basic meanings overlap.
4. Do not confuse feasibility with certainty. A feasible plan may still fail for other reasons.
5. Use a simple alternative when needed. “Not feasible” is clear and widely understood.

These reminders will help you choose the right wording without overthinking the difference.

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Fill in the Blanks

Choose unfeasible, infeasible, or feasible to complete each sentence.

1. The project cannot be completed with our current budget, so it is ______.
2. The team has enough time and money to finish the plan, making it ______.
3. The engineers decided that the original design was ______.
4. Completing all the work in five minutes would be ______.
5. Both ______ and ______ are accepted English words meaning not feasible.

Answers:

1. infeasible (unfeasible is also correct)
2. feasible
3. infeasible (unfeasible is also correct)
4. unfeasible (infeasible is also correct)
5. unfeasible; infeasible

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Mini Quiz

1. Which statement is correct?

A. Only infeasible is a real word.
B. Only unfeasible is a real word.
C. Both words are correct.

Answer: C. Both words are correct.

2. What does infeasible mean?

A. Easy to complete
B. Not practical or achievable
C. Already completed

Answer: B. Not practical or achievable.

3. Which word is often used in technical writing?

A. Infeasible
B. Feasibly impossible
C. Unfeasibilityable

Answer: A. Infeasible. Unfeasible is also acceptable in many technical contexts.

4. What is the opposite of feasible?

A. Feasibility
B. Infeasible
C. Feasibly

Answer: B. Infeasible. Unfeasible also expresses the opposite of feasible.

5. Which phrase can replace both words in many sentences?

A. Not feasible
B. Very possible
C. Already finished

Answer: A. Not feasible.

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FAQs

1. Is unfeasible or infeasible correct?

Both words are correct. They mean that something is not feasible or cannot realistically be achieved.

2. Is unfeasible a misspelling of infeasible?

No. Unfeasible is an accepted English word. It is not a misspelling of infeasible.

3. Do unfeasible and infeasible mean the same thing?

Yes, they have the same basic meaning and are usually interchangeable. Both describe something that is not practical or achievable.

4. Which word is better for formal writing?

Both can be used in formal writing. Infeasible is common in technical and academic contexts, but unfeasible is also correct.

5. What is the opposite of infeasible?

The opposite is feasible, which means possible or practical to achieve.

6. Can I write “not feasible” instead?

Yes. “Not feasible” is a clear and natural phrase that works in everyday, academic, and professional writing.

7. Does unfeasible mean impossible?

It can describe something that cannot be done in practice. However, the problem may be temporary. A plan might become feasible if the available time, money, or resources change.

8. Which word is more common: unfeasible or infeasible?

Usage varies by period and context. Infeasible is often more common in contemporary formal and technical writing, but both forms remain accepted.

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Conclusion

When choosing between unfeasible or infeasible, remember that both spellings are correct. They share the same basic meaning: something is not practical or cannot reasonably be achieved. Neither word is a misspelling, and neither has a completely separate meaning that you must memorize.

Infeasible is often used in technical, academic, and professional writing, while unfeasible is also accepted in everyday and formal English. Your choice can depend on context, style, and personal preference. If you want the simplest option, use not feasible.

The most important rule is to focus on the meaning rather than worry that one spelling is wrong. Understanding both forms will help you write more clearly and confidently.

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