Choosing the correct spelling can be tricky when two forms sound similar. In modern English, mistakenly is the standard adverb and the natural choice. It comes from the verb mistake and describes an error caused by an incorrect belief. Meanwhile, mistakingly is a rare and unusual form that readers may notice.
This confusion often appears in online writing, messages, and everyday speech. Therefore, understanding the difference helps English learners use the word confidently. In standard English, mistakenly is the established choice for polished writing. This guide explains usage, meaning, and common patterns through clear examples. It also shows where mistakingly may appear and why readers expect mistakenly.
Quick Answer
Mistakenly is the correct and standard spelling when you need an adverb meaning “in error,” “wrongly,” or “because of a mistake.”
Use mistakenly when:
- You did something because you were wrong.
- You believed something that wasn’t true.
- You identified someone or something incorrectly.
- You performed an action in error.
- You want a standard adverb for formal or everyday English.
Examples:
- I mistakenly deleted the file.
- She mistakenly believed the meeting started at noon.
- He mistakenly sent the invoice to the wrong customer.
- They mistakenly identified the building as the hotel.
- I mistakenly thought you had already left.
Cambridge defines mistakenly as an adverb meaning “wrongly or by mistake.” Oxford gives the related sense of doing something in a way based on a wrong opinion or poor judgment.
By contrast, mistaking is the -ing form of the verb mistake.
For example:
She was mistaking him for his brother.
That sentence is completely different from:
She mistakenly thought he was his brother.
So the quick rule is simple:
Use “mistakenly” for the adverb. Use “mistaking” when you need the -ing form of the verb.
Comparison Overview
The easiest way to understand mistakingly or mistakenly is to compare their grammatical jobs.
| Word | Part of speech | Main meaning | Standard use | Example |
| mistakenly | Adverb | In error or wrongly | Standard | I mistakenly called the wrong number. |
| mistaking | Verb form / present participle | Confusing one thing with another | Standard | She was mistaking me for someone else. |
| mistaken | Adjective / past participle | Wrong in belief or judgment | Standard | I was mistaken about the date. |
| mistake | Noun / verb | An error or to judge incorrectly | Standard | Everyone makes a mistake. |
| mistook | Past-tense verb | Judged or identified incorrectly | Standard | I mistook him for his brother. |
This distinction matters because English doesn’t build every adverb by simply attaching -ly to the most obvious verb form.
The verb mistake has several forms:
- mistake — present form
- mistook — past tense
- mistaken — past participle
- mistaking — -ing form
The standard adverb comes from mistaken, producing mistakenly. Oxford lists mistakenly as an adverb and separately identifies mistaking as the -ing form of mistake.
Main Differences Between Mistakingly or Mistakenly
The biggest difference isn’t really between two equally accepted spellings. Instead, it involves a standard adverb versus a verb form that looks like it could become an adverb.
Mistakenly describes an action done in error
Consider this sentence:
I mistakenly attached the wrong document.
The word mistakenly tells the reader how the action happened. The speaker attached the wrong document because of an error.
You could also say:
I attached the wrong document by mistake.
Both sentences communicate essentially the same situation.
Cambridge specifically gives by mistake as meaning “by accident” or unintentionally.
Mistaking describes the act of confusing something
Now consider:
I was mistaking the blue folder for the green one.
Here mistaking doesn’t mean “in an erroneous way” as an adverb. It functions as the -ing form of the verb mistake.
The sentence describes an ongoing act of confusing one thing with another.
The same structure appears in:
She was mistaking my brother for me.
They were mistaking the warning sign for an advertisement.
He kept mistaking the two addresses.
Oxford and Cambridge both document the construction mistake someone or something for someone or something.
The simplest test
Ask yourself what role the word needs to play.
If you could replace the word with “wrongly” or “by mistake,” use mistakenly.
If you could replace it with “confusing one thing with another,” you probably need mistaking.
For example:
She mistakenly entered the wrong room.
The replacement works:
She wrongly entered the wrong room.
Now consider:
She was mistaking the office for the conference room.
Here the replacement does not work naturally:
She was wrongly the office for the conference room.
The grammar gives you the answer.
Read More: Freshman or Freshmen: Which Is Correct? A Complete Grammar and Usage Guide
Why “Mistakingly” Looks So Plausible
There is a perfectly reasonable-looking pattern behind this common error.
English has many adverbs that come from words ending in -ing or from present participles:
- surprisingly
- knowingly
- willingly
- knowingly
- unwillingly
- increasingly
- misleadingly
Because of that pattern, mistakingly can look perfectly logical.
There is another reason for the confusion. The verb mistake genuinely produces mistaking:
He is mistaking the signal for a warning.
A reader who knows that mistaking is correct may naturally assume that adding -ly creates the adverb.
English doesn’t always work that neatly.
The standard adverb is mistakenly because it follows the established adjective and participial form mistaken.
This is one of those cases where English vocabulary behaves more like a historical patchwork than a perfectly engineered system.
What Does “Mistakenly” Mean?
Mistakenly means that someone does something wrongly because of an error, incorrect belief, misunderstanding, or bad judgment.
Cambridge’s examples include situations where someone incorrectly believes something or performs an action because of an error.
Here are several common meanings.
Doing something by error
I mistakenly deleted the original photograph.
The deletion wasn’t necessarily intentional. The person made an error.
Believing something incorrectly
She mistakenly believed that the store was open.
The problem lies in her belief rather than necessarily in her physical action.
Identifying something incorrectly
The witness mistakenly identified the wrong vehicle.
The person made an incorrect identification.
Making an incorrect assumption
We mistakenly assumed that the contract had already been signed.
The word highlights the incorrect assumption.
This makes mistakenly especially useful in professional writing. It can describe an error without making the sentence unnecessarily dramatic.
What Does “Mistaking” Mean?
Mistaking is the present participle or gerund form of mistake.
The verb mistake can mean to understand or identify someone or something incorrectly. Oxford lists mistaking as the -ing form of the verb.
For example:
You are mistaking my silence for agreement.
The person isn’t merely doing something “mistakenly.” They are confusing one thing with another.
Another example:
He was mistaking the shadow for a person.
The speaker describes an ongoing process of incorrect identification.
This distinction becomes particularly useful with the construction mistake A for B.
Common pattern
mistake + person or thing + for + person or thing
Examples include:
- I mistook her for her sister.
- She mistook the noise for an alarm.
- They mistook the restaurant for a hotel.
- He is mistaking confidence for arrogance.
- You may be mistaking correlation for causation.
The final example demonstrates why mistaking remains important. It has a legitimate grammatical function that mistakenly cannot replace.
Mistakenly vs. Mistaken
Another common source of confusion involves mistakenly and mistaken.
They are related but perform different grammatical jobs.
Mistakenly functions as an adverb.
She mistakenly entered the wrong address.
Mistaken can function as an adjective.
She was mistaken about the address.
The difference becomes clearer when you examine what each word modifies.
In the first sentence, mistakenly modifies the action entered.
In the second sentence, mistaken describes the person’s state of belief or judgment.
Cambridge defines mistaken as being wrong in what you believe or as something based on an incorrect belief.
Compare these examples
| Sentence | What it means |
| I mistakenly entered the wrong room. | I entered it because of an error. |
| I was mistaken about the room number. | My belief about the room number was wrong. |
| I mistook the office for a classroom. | I identified the office incorrectly. |
| I was mistaking the office for a classroom. | I was in the process of making that confusion. |
These sentences overlap in meaning. Their grammar remains different.
Mistakenly vs. By Mistake
In many sentences, mistakenly and by mistake can replace each other naturally.
Consider:
I mistakenly sent the email to Sarah.
You could also say:
I sent the email to Sarah by mistake.
The first version is compact. The second version sounds especially natural in everyday conversation.
When “mistakenly” works well
Use mistakenly when you want a concise adverb.
The payment was mistakenly processed twice.
The article mistakenly identified the author.
The customer was mistakenly charged for two items.
When “by mistake” works well
Use by mistake when you’re speaking casually or explaining an accidental action.
I opened your message by mistake.
I called the wrong number by mistake.
and I took your umbrella by mistake.
Neither construction needs to sound stiff. The surrounding sentence usually determines the tone.
Mistakenly vs. Accidentally
These words often overlap. They aren’t always interchangeable.
Accidentally focuses strongly on unintended action.
Mistakenly focuses more strongly on error, incorrect belief, or incorrect judgment.
Compare:
I accidentally deleted the photograph.
This emphasizes that the deletion was unintended.
Now consider:
I mistakenly deleted the photograph.
This emphasizes that the deletion resulted from an error.
The difference can be subtle. Context often matters more than the dictionary distinction.
Consider another pair:
I accidentally called your number.
The call happened unintentionally.
I mistakenly called your number.
The speaker likely believed they were calling someone else.
That small shift in emphasis can make a sentence more precise.
Mistakingly or Mistakenly in American English
For standard American English, mistakenly is the form to use when you need this adverb.
There is no standard American spelling rule that changes mistakenly into mistakingly.
The same preferred form appears in American dictionary resources. Cambridge’s American Dictionary entry gives examples such as people who “mistakenly believe” something.
That matters because spelling questions sometimes get incorrectly framed as American English versus British English debates.
This isn’t one of those cases.
The distinction between mistakenly and mistakingly isn’t comparable to familiar differences such as:
- color / colour
- organize / organise
- center / centre
Those represent recognized regional spelling differences.
Mistakenly doesn’t belong to that category.
Mistakingly or Mistakenly in British English
British English also uses mistakenly as the standard adverb.
Oxford’s learner dictionary gives mistakenly as an adverb meaning that something is done because of a wrong opinion or poor judgment.
So both major varieties of English align here:
| Variety | Standard adverb |
| American English | mistakenly |
| British English | mistakenly |
| Formal international English | mistakenly |
The spelling does not need to change when you switch between American and British English.
Is “Mistakingly” a Real Word?
This question needs a little nuance.
You may encounter mistakingly in real-world writing. Search engines can find occurrences of almost any unusual construction because people publish enormous amounts of unedited text online.
That doesn’t automatically make the form a preferred standard word.
The important distinction is between attested usage and standard recommended usage.
A form can appear somewhere without being the form you should choose in careful writing.
For practical purposes, writers who need standard contemporary English should use mistakenly.
This is especially true for:
- school assignments
- professional emails
- reports
- resumes
- articles
- business communication
- academic writing
- edited publications
- formal documents
If a reader sees mistakingly, they may understand your meaning. They may still recognize it as unusual or nonstandard.
Why create that speed bump when mistakenly is clear and established?
Common Mistakes With Mistakingly and Mistakenly
Mistake 1: Using “mistakingly” as the adverb
Incorrect or nonstandard:
I mistakingly sent the wrong attachment.
Preferred:
I mistakenly sent the wrong attachment.
The second sentence uses the established adverb.
Mistake 2: Confusing “mistaking” with “mistakenly”
Incorrect:
She mistakenly him for his sister.
Preferred:
She was mistaking him for his sister.
Or:
She mistakenly thought he was his sister.
The problem here isn’t just spelling. The sentence needs a verb structure that works grammatically.
Mistake 3: Using “mistaken” where an adverb is needed
Awkward:
He mistaken entered the wrong room.
Correct:
He mistakenly entered the wrong room.
Mistaken describes a person or belief. Mistakenly modifies an action.
Mistake 4: Assuming every -ing form can become an -ing + -ly adverb
English doesn’t operate through a universal “add -ly” formula.
Some words follow patterns that learners can predict. Others have established forms that must be learned individually.
That’s why mistakenly should be treated as the standard lexical choice rather than reconstructed as mistakingly.
Mistakingly or Mistakenly: Everyday Examples
Here are practical examples you can use as a reference.
| Intended meaning | Preferred sentence |
| Sent something to the wrong person | I mistakenly sent the message to John. |
| Entered the wrong room | She mistakenly entered Room 204. |
| Believed something incorrectly | He mistakenly believed the store was closed. |
| Charged someone incorrectly | The customer was mistakenly charged twice. |
| Deleted something in error | I mistakenly deleted the file. |
| Confused two people | I was mistaking him for his brother. |
| Confused two objects | She was mistaking the copy for the original. |
| Held an incorrect belief | I was mistaken about the deadline. |
| Identified someone incorrectly | I mistook her for my old coworker. |
Notice how the correct choice depends on the grammar.
That is more useful than simply memorizing “mistakenly is correct.”
A Practical Case Study: The Wrong Email Attachment
Imagine that an employee sends a confidential spreadsheet to the wrong colleague.
Several sentences could describe the event:
I mistakenly sent the spreadsheet to David.
This is concise and professional.
I sent the spreadsheet to David by mistake.
This sounds more conversational.
I accidentally sent the spreadsheet to David.
This emphasizes the unintended nature of the action.
Now imagine the employee thought David was the intended recipient:
I mistakenly believed David was handling the project.
Here mistakenly describes an incorrect belief.
Now change the situation:
I was mistaking David for Daniel.
This means the employee was confusing one person with another.
One small change in grammar creates a different meaning. That’s why choosing between these forms requires more than checking the spelling.
How to Remember the Difference
A simple mental shortcut can save you from the entire mistakingly or mistakenly problem.
Use this three-word test:
Wrong action? → mistakenly
Confusing two things? → mistaking
Wrong belief? → mistaken
For example:
I mistakenly chose the wrong file.
Wrong action.
I was mistaking the wrong file for the original.
Confusion between two things.
I was mistaken about which file was original.
Wrong belief.
This method works because it focuses on the role of the word rather than its appearance.
Where “Mistakenly” Goes in a Sentence
Because mistakenly is an adverb, it can appear in several positions.
Before the main verb
She mistakenly entered the wrong address.
This is probably the clearest structure.
After an auxiliary verb
She had mistakenly entered the wrong address.
The adverb fits naturally between the auxiliary and main verb.
After the main verb
She entered the wrong address mistakenly.
This is grammatically possible in some contexts. It can sound less natural than placing the adverb earlier.
At the beginning for emphasis
Mistakenly, I assumed the appointment was tomorrow.
This construction is grammatical. It sounds more deliberate and formal.
In ordinary conversation, most speakers will prefer a more natural placement:
I mistakenly assumed the appointment was tomorrow.
Good writing isn’t only about grammatical possibility. It is also about choosing the position that sounds effortless.
Common “Mistakingly or Mistakenly” Corrections
Here are several quick corrections worth remembering.
| Less suitable wording | Better wording | Reason |
| I mistakingly sent it. | I mistakenly sent it. | Use the standard adverb. |
| She mistakingly believed him. | She mistakenly believed him. | Mistakenly modifies believed. |
| He mistaken entered the room. | He mistakenly entered the room. | The sentence needs an adverb. |
| I was mistakenly him for Tom. | I was mistaking him for Tom. | The -ing verb form is required. |
| I was mistaken him for Tom. | I mistook him for Tom. | Mistook is the past tense. |
| I was mistaken about him. | Correct. | Mistaken works as an adjective here. |
The pattern becomes much easier once you stop treating these forms as interchangeable spellings.
They aren’t.
Frequently Asked Questions
Is mistakenly the correct spelling?
Yes, mistakenly is the correct spelling and the standard adverb in modern English. It means doing something because of an incorrect belief or error.
Is mistakingly a correct English word?
Mistakingly is an attested word, but it is rare and unusual. In most standard English writing, mistakenly is the natural choice.
What is the difference between mistakenly and mistakingly?
The main difference is usage rather than meaning. Mistakenly is the established form that readers expect in everyday writing, while mistakingly appears far less often.
Can I use mistakenly in professional writing?
Yes, mistakenly works well in professional emails, formal documents, and other polished writing. It is also common in everyday messages and online writing.
How can English learners remember the correct usage?
Remember that mistakenly comes from the verb mistake and acts as a standard adverb. Therefore, use mistakenly confidently when describing an action caused by an incorrect belief.
Final Takeaway
In short, mistakenly is the correct spelling and the standard choice in modern English. While mistakingly may appear in rare usage, mistakenly fits everyday writing, professional messages, and formal contexts more naturally. Therefore, choosing mistakenly helps avoid confusion and makes your usage clear, accurate, and confident.
