Mistakingly or Mistakenly: Which Word Is Correct?

If you are wondering whether mistakingly or mistakenly is correct, the best choice in modern standard English is mistakenly. It means “wrongly,” “incorrectly,” or “by mistake.” For example, you would write, “I mistakenly sent the email to the wrong person.” Mistakingly does exist in some dictionaries and historical usage, but it is uncommon and is not the natural choice for most modern writing.

This distinction matters because mistakingly looks perfectly logical. English has the verb mistake, the -ing form mistaking, and many adverbs ending in -ly. That can make mistakingly seem like the obvious form. However, English word formation is not always predictable. In ordinary school, business, academic, and everyday writing, mistakenly is the clear and reliable choice.

Quick Answer: Mistakingly or Mistakenly?

Mistakenly is the standard and preferred word in modern English when you mean “by mistake,” “wrongly,” or “incorrectly.” Cambridge Dictionary defines mistakenly as “wrongly or by mistake.”

Examples:

• I mistakenly deleted the file.
• She mistakenly thought the meeting was tomorrow.
• The package was mistakenly delivered to the wrong address.

Memory tip: If you can replace the word with “by mistake,” use mistakenly.

What Does Mistakenly Mean?

Mistakenly is an adverb. It describes an action, belief, judgment, statement, or decision that was wrong or made because of an error.

Cambridge Dictionary gives the meanings “wrongly” and “by mistake.” Dictionary.com similarly defines it as “unintentionally or inadvertently; by mistake” and “in a way that is wrongly conceived, held, or done; incorrectly.”

Mistakenly Meaning “By Mistake”

When something happens accidentally because of an error, mistakenly can describe what happened.

• I mistakenly sent the invoice to the wrong client.
• She mistakenly opened my email.
• The employee mistakenly entered the wrong number.
• We mistakenly booked the meeting room for Friday.

In each example, the person did something incorrectly.

Mistakenly Meaning “Wrongly”

Mistakenly can also describe a belief or conclusion that is incorrect.

• He mistakenly believed the store was closed.
• They mistakenly assumed that the deadline had been extended.
• She mistakenly thought I was referring to another document.

Here, the problem is not necessarily an accidental physical action. The person simply had an incorrect belief or understanding.

Key takeaway: Mistakenly can describe both an incorrect action and an incorrect belief or judgment.

Why Do People Write Mistakingly?

The main reason is that mistakingly looks as though it follows a logical English pattern.

Consider these related forms:

A writer may see mistaking and naturally assume that adding -ly should produce mistakingly. That reasoning is understandable, but it does not reflect the standard modern form.

The usual adverb is based on mistaken + -ly, giving mistakenly. Dictionary.com explicitly lists its formation as mistaken + -ly.

English Does Not Always Follow a Perfect Formula

English contains many word forms that cannot be predicted simply by adding an ending.

For example:

• good → well
• fast → fast
• public → publicly
• basic → basically

This is why a word can look grammatically possible without being the normal word used by modern speakers and writers.

Practical lesson: Do not create an adverb simply because adding -ly appears logical. Check the established form when the spelling is uncertain.

Is Mistakingly a Word?

Yes, but this needs an important qualification.

Mistakingly is an attested English word. It appears in some dictionaries and historical sources. Dictionary.com has an entry for mistakingly, and older dictionaries also recorded it with meanings such as “erroneously” or “falsely.”

That means it is too strong to say that mistakingly is completely imaginary or that nobody has ever used it.

However, existence does not make a word the best choice for modern standard writing.

In normal contemporary English, mistakenly is the form readers expect. It is the form supported by current mainstream dictionary usage and is widely used in everyday, professional, academic, and published writing. Cambridge, for example, gives numerous modern examples of mistakenly in use.

What Should Modern Writers Do?

If your goal is clear, natural English, choose mistakenly.

Use mistakingly only if you have a specific historical, literary, or source-based reason to reproduce that unusual form.

Key takeaway: Mistakingly exists, but mistakenly is the practical standard choice.

Mistakenly vs. Accidentally

A related question is whether mistakenly and accidentally mean exactly the same thing. They can overlap, but they often emphasize different ideas.

Consider these two sentences:

I mistakenly sent the report to Sarah.

This suggests that Sarah was the wrong recipient and the sender made an error.

I accidentally sent the report to Sarah.

This emphasizes that sending it to Sarah was unintended.

Sometimes either word works, but the emphasis changes.

A Simple Substitution Test

Ask:

Does “by mistake” make sense?

• I mistakenly chose the wrong file.
• I chose the wrong file by mistake.

Yes. That strongly supports mistakenly.

Now consider:

• I accidentally dropped my phone.
• I dropped my phone by mistake.

The second sentence is possible in some contexts, but accidentally is more natural because the event was an unintended physical action rather than an incorrect judgment.

Expert tip: Use mistakenly when the important idea is error or incorrect understanding. Use accidentally when the important idea is unintended occurrence.

Mistakenly or Mistakingly in Different Contexts

The safest choice remains mistakenly, regardless of the setting.

Professional and Business Writing

In professional communication, clarity matters more than choosing an unusual word.

Prefer:

The payment was mistakenly processed twice.

Avoid:

The payment was mistakingly processed twice.

The first version sounds natural and immediately communicates that an error occurred.

Academic Writing

Academic writers often use mistakenly when discussing incorrect assumptions, interpretations, or classifications.

For example:

The results were mistakenly interpreted as evidence of a causal relationship.

This is especially useful when the issue is not a physical accident but an incorrect interpretation.

Common Mistakes With Mistakingly and Mistakenly

Mistake 1: Assuming Mistakingly Is the Normal Form

Incorrect for standard modern usage:

She mistakingly identified the wrong person.

Better:

She mistakenly identified the wrong person.

The first version may be understood, but the second is the natural modern choice.

Mistake 2: Building the Adverb From Mistaking

Some writers reason:

mistake → mistaking → mistakingly

The problem is that English does not guarantee that every grammatical form can be turned into an adverb by adding -ly.

The established form is:

mistaken → mistakenly

Mistake 3: Assuming “Mistakingly” Is Completely Impossible

The opposite extreme is also inaccurate.

Because mistakingly has historical and dictionary evidence, calling it “not a word” oversimplifies the issue.

The more useful distinction is:

Possible/attested word ≠ preferred modern word.

For practical writing, choose mistakenly.

Mistake 4: Using Mistakenly When Accidentally Is More Precise

Not every unintended event involves a mistake in belief or judgment.

I accidentally spilled coffee on the contract.

This is usually more natural than:

I mistakenly spilled coffee on the contract.

The first sentence describes an unintended accident. The second can suggest that the person made an incorrect choice, which is not the intended meaning.

A Quick Decision Guide

When you are unsure which form to use, follow this process:

Do you mean “wrongly,” “incorrectly,” or “by mistake”?

↓

Yes

↓

Use mistakenly.

Example:
“I mistakenly entered the wrong address.”

Are you describing something that happened unintentionally rather than an error in judgment?

↓

Use accidentally when it better expresses the meaning.

Example:
“I accidentally dropped the glass.”

Are you reproducing an old text or discussing historical vocabulary?

↓

Mistakingly may be relevant if the original source actually uses it.

This framework prevents two different problems: choosing the unusual mistakingly simply because it looks logical, and using mistakenly when accidentally is more precise.

Mistakenly in Real-Life Sentences

Seeing the word in different situations makes its function easier to understand.

Business

The customer was mistakenly charged twice.

The word explains that the duplicate charge resulted from an error.

Education

The student mistakenly copied the wrong answer from the board.

The action was based on a mistake.

Email

I mistakenly attached the earlier version of the report.

This is a natural way to acknowledge an error professionally.

Daily Conversation

I mistakenly thought you lived in Chicago.

Here, the mistake concerns a belief rather than an action.

Technology

The file was mistakenly deleted during the update.

The deletion was unintended and resulted from an error.

Professional Editing

The article mistakenly identifies the two terms as synonyms.

This use is particularly useful when explaining an incorrect statement or interpretation.

How to Remember the Correct Spelling

The easiest memory trick is:

Mistaken → Mistakenly

Think of the adjective mistaken first.

mistaken + ly = mistakenly

Do not build the word from mistaking.

Another useful test is the “by mistake” test:

I mistakenly called her.
I called her by mistake.

If the second sentence preserves the intended meaning, mistakenly is usually the right choice.

Mini Quiz

Choose the better word:

1. I ______ thought the appointment was at 3 p.m.
2. The document was ______ uploaded twice.
3. He ______ dropped the glass while reaching for his phone.
4. The report ______ described the two products as identical.

Answers:

1. mistakenly
2. mistakenly
3. accidentally
4. mistakenly

The first, second, and fourth sentences focus on an error or incorrect understanding. The third focuses on an unintended physical event.

Frequently Asked Questions

Is “mistakingly” grammatically correct?

Mistakingly is an attested English word and has appeared in dictionaries and historical usage. However, it is rare in modern English. For ordinary contemporary writing, mistakenly is the preferred form.

Is “mistakenly” a real word?

Yes. Mistakenly is a standard adverb meaning “wrongly,” “incorrectly,” or “by mistake.” Cambridge Dictionary lists it as an adverb and provides current examples of its use.

Can I use “mistakingly” in formal writing?

It is better to avoid it unless you have a specific reason to use the historical or rare form. In formal writing, mistakenly will be clearer and more familiar to readers.

Why does “mistakingly” sound logical?

It looks as though it is formed from mistaking + -ly. Because mistaking is a legitimate form of mistake, the construction can seem natural. But the established modern adverb is mistakenly, formed from mistaken + -ly.

Is “mistakenly” the same as “wrongly”?

They are often interchangeable, but not always identical in tone. Wrongly directly emphasizes that something is incorrect, while mistakenly often suggests that an error or misunderstanding caused the incorrect action or belief.

Is “mistakenly” the same as “accidentally”?

Not always. Mistakenly commonly focuses on an error, wrong belief, or incorrect choice. Accidentally focuses more broadly on something happening unintentionally.

Which is better: “I mistakenly did it” or “I did it mistakenly”?

Both can be grammatically possible, but “I mistakenly did it” is generally more natural when the adverb describes the action. In many cases, rewriting the sentence can make the meaning even clearer.

Can “mistakenly” describe a belief?

Yes. This is one of its common uses.

She mistakenly believed that the store was closed.

Here, the person did not necessarily perform an accidental action. Her belief was simply incorrect.

Should students use “mistakenly” in essays?

Yes. Mistakenly is appropriate in academic and school writing when you need to explain an incorrect assumption, interpretation, identification, or action.

What is the easiest way to remember “mistakenly”?

Remember:

mistaken + ly = mistakenly

Then use the “by mistake” test. If “by mistake” fits naturally, mistakenly is usually the word you need.

Key Takeaways

• Mistakenly is the standard and preferred choice in modern English.
• It means wrongly, incorrectly, or by mistake.
• Mistakingly is an attested but uncommon form.
• Do not assume mistakingly is completely nonexistent; its issue is mainly modern usage and preference.
• In school, academic, business, professional, and everyday writing, choose mistakenly.
• Mistakenly and accidentally can overlap, but they do not always emphasize the same idea.
• Remember the formation: mistaken + -ly = mistakenly.

Editorial Note

For practical modern English, the safest editorial recommendation is simple: use “mistakenly” unless you have a specific historical or source-based reason to use “mistakingly.”

This distinction is more useful than simply labeling mistakingly “wrong.” A rare word can be real while still being a poor choice for ordinary modern writing.

References

• Cambridge Dictionary — “mistakenly”
• Dictionary.com — “mistakenly”
• Dictionary.com — “mistakingly”
• Webster’s 1828 Dictionary — “mistakingly”

Conclusion

When choosing between mistakingly or mistakenly, choose mistakenly for almost every modern English sentence. It is the familiar adverb used for something done wrongly, incorrectly, or by mistake.

Although mistakingly has a history and can be found in dictionary records, it is unusual enough to distract readers in normal writing. You do not gain a useful meaning by choosing it.

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