Definitely is the correct spelling, while definatly is a common misspelling that should be avoided in standard English. If you’ve seen both “definitely” and “definatly” and wondered which one is correct, the confusion usually comes from the way the word is pronounced and the fact that its spelling contains several vowels that are easy to mix up.
The definitely vs definatly distinction is simple: definitely is the standard and correct spelling, while definatly is incorrect. The word definitely is an adverb meaning certainly, without doubt, or clearly. It is commonly used to express strong certainty about something. Related words and expressions include certainly, surely, unquestionably, absolutely, and without a doubt.
In this guide, you’ll learn whether “definitely” or “definatly” is correct, what “definitely” means, why “definatly” is misspelled, and how to use the correct spelling in sentences. You’ll also see clear examples and simple memory tips to help you remember the spelling.
By the end, you’ll know exactly how to spell definitely correctly, why definatly is wrong, and how to use definitely naturally and confidently in your writing.
Definitely vs Definatly: Quick Answer
The correct spelling is definitely.
Definatly is a misspelling and is not the standard spelling of the word.
| Word | Correct? | Meaning |
| Definitely | Yes | Certainly; without doubt |
| Definatly | No | Misspelling of definitely |
| Defiantly | Yes, but different | In a way that shows resistance or disobedience |
For example:
I will definitely finish the report today.
Here, definitely means that the speaker is certain about finishing the report.
The following sentence contains the common spelling error:
I will definatly finish the report today.
The meaning is understandable, but definatly should be replaced with definitely in standard written English.
Cambridge Dictionary defines definitely as an adverb meaning “without any doubt,” while Oxford describes it as a word used to emphasize that something is true and that there is no doubt about it.
Why Is Definitely Correct?
The easiest way to understand the spelling is to look at the word from which it is formed.
Definitely comes from:
definite + -ly = definitely
The adjective definite already contains the sequence finite:
de + finite
When -ly is added, the spelling becomes:
definite → definitely
That gives you the important spelling pattern:
definite → definitely
The incorrect spelling definatly changes the i in definite to an a and also leaves out the e before the final -ly structure.
The Correct Spelling of Definitely
The correct form contains these letters:
D-E-F-I-N-I-T-E-L-Y
It has 10 letters.
A useful way to see its structure is:
DEFINITE + LY
The word definite is spelled:
D-E-F-I-N-I-T-E
Adding -ly produces:
D-E-F-I-N-I-T-E-L-Y
This spelling remains consistent in both American and British English. There is no standard American-versus-British spelling difference in which one variety uses definatly.
Why Definatly Is Incorrect
Definatly is an error rather than an alternative spelling.
The problem usually comes from how the word is heard and remembered. In normal speech, unstressed vowels can be less prominent than they appear in writing. As a result, a writer may remember the sound approximately and reconstruct the spelling as definatly.
Another issue is that English spelling does not always allow you to predict every letter simply from pronunciation.
Compare:
- definite
- definitely
- definately
- definatly
Only the first two are standard forms of this word family.
The important point is that definatly does not become correct simply because readers understand what the writer means. In edited writing, spelling should follow the established standard form.
Definitely Meaning and Definition
Definitely is an adverb that usually means certainly, without doubt, or without any uncertainty.
Cambridge gives the central meaning as “without any doubt.” Oxford similarly explains that the word can emphasize that something is true and that there is no doubt about it.
For example:
She definitely knows the answer.
This means the speaker is confident that she knows the answer.
Another example is:
We are definitely going to the concert.
The speaker is expressing certainty about the plan.
Definitely as a Word of Certainty
One of the most common uses of definitely is to strengthen a statement.
Compare:
- I think I will go.
- I will probably go.
- I will definitely go.
These sentences communicate different degrees of certainty.
Definitely places the statement at the strongest end of this particular scale. The speaker is presenting the action as certain rather than merely possible or probable.
Consider these examples:
- I will definitely call you tomorrow.
- She definitely passed the exam.
- They are definitely coming to dinner.
- This is definitely the correct address.
- He definitely said that he would help.
In each case, definitely tells the reader or listener that the speaker has a high level of certainty.
Definitely as a Short Answer
You can also use definitely by itself as a response.
For example:
“Would you like to come with us?”
“Definitely!”
Here, the word functions as a complete affirmative response. Cambridge notes that definitely is often used for emphasis, particularly in speech.
It can also be used negatively:
Definitely not.
This means the speaker is expressing strong certainty that something will not happen or is not acceptable.
For example:
“Are you going to buy that expensive laptop?”
“Definitely not.”
How Definitely Is Used in a Sentence
Because definitely is an adverb, it can modify a verb, adjective, or an entire statement depending on its position and context.
Consider:
I definitely remember her name.
Here, definitely strengthens the speaker’s claim that they remember the name.
Now compare:
The answer is definitely correct.
In this sentence, definitely strengthens the assertion that the answer is correct.
It can also appear before a negative:
I definitely do not agree.
This makes the disagreement especially clear.
Common Sentence Patterns With Definitely
Several patterns occur naturally in everyday English.
Definitely + verb
She definitely understands the problem.
Subject + definitely + auxiliary verb + main verb
They definitely will attend the meeting.
Definitely + adjective
That was definitely unusual.
Definitely + negative expression
He is definitely not ready.
Definitely as a standalone response
“Are you coming?”
“Definitely.”
Oxford’s examples show similar uses, including “definitely not” and statements in which the word emphasizes certainty.
Definitely vs Definatly Examples
The clearest way to understand the difference is to put the two forms side by side.
| Incorrect | Correct |
| I will definatly call you. | I will definitely call you. |
| She definatly knows the answer. | She definitely knows the answer. |
| We are definatly going tomorrow. | We are definitely going tomorrow. |
| He definatly needs more time. | He definitely needs more time. |
| That is definatly the right choice. | That is definitely the right choice. |
In every pair, the intended meaning remains clear. The problem is the spelling.
Correct Examples With Definitely
Here are more examples showing how definitely works in different contexts:
- I definitely want to visit New York someday.
- She definitely deserves the promotion.
- You should definitely read this book.
- We definitely need more time to finish the project.
- He definitely remembers meeting you.
- That restaurant is definitely worth trying.
- I would definitely recommend this approach.
- They definitely made the right decision.
- This is definitely not what I expected.
- She definitely did not say that.
Notice that the word does not change its spelling according to the context.
Whether the sentence is formal, conversational, positive, negative, or emphatic, the standard spelling remains definitely.
Definitely vs Defiantly: What Is the Difference?
The distinction between definitely and defiantly is especially important because both words look similar.
Unlike definatly, defiantly is a real English word. However, it has an entirely different meaning.
What Does Definitely Mean?
Definitely means certainly, without doubt, or unquestionably.
Example:
She will definitely attend the meeting.
The speaker is certain that she will attend.
Another example:
I definitely saw him at the store.
The speaker is emphasizing certainty about what they saw.
What Does Defiantly Mean?
Defiantly is the adverbial form of defiant.
It describes behavior that shows resistance, opposition, or refusal to obey.
For example:
The student defiantly refused to leave the classroom.
Another example:
He defiantly ignored the warning.
The action is described as resistant or disobedient.
Definitely vs Defiantly Examples
Compare these sentences:
She definitely agreed with the plan.
This means there is no doubt that she agreed.
She defiantly rejected the plan.
This means she rejected it in a resistant or challenging manner.
The difference is therefore semantic, not merely orthographic.
| Word | Meaning | Example |
| Definitely | Certainly; without doubt | I will definitely be there. |
| Defiantly | In a resistant or disobedient manner | He defiantly refused to apologize. |
| Definatly | Incorrect spelling | Do not use this form in standard writing. |
A useful memory cue is:
definitely = certainty
defiantly = defiance
The words are related visually, but they communicate completely different ideas.
How to Remember the Spelling of Definitely
The spelling becomes easier when you stop trying to memorize all ten letters as one long sequence.
Instead, remember the word definite.
DEFINITE + LY = DEFINITELY
That is the most useful spelling pattern.
Remember “Finite” Inside Definitely
Another useful trick is to notice the word finite inside definite:
de + finite + ly
The word therefore contains finite:
definitely
This helps prevent the common a error in definatly.
You can use the memory sentence:
“Finite is definitely inside definitely.”
The important spelling is:
finite → definite → definitely
Remember That Definitely Has an “I”
If you are choosing between:
- definatly
- definitely
remember that definitely comes from definite, which contains i.
So:
❌ definatly
✅ definitely
The same principle helps distinguish definitely from definately:
❌ definately
✅ definitely
A Quick Spelling Check
When writing the word, pause after defin:
defin + itely
Then check the complete form:
definitely
A stronger method is simply to think:
definite + ly
That avoids relying on pronunciation.
Common Spelling Mistakes With Definitely
Definitely is frequently misspelled because several forms look or sound plausible.
The most relevant mistakes include definatly, definately, and definitly.
Definatly
Definatly is incorrect.
The writer has changed the vowel pattern and omitted the e found in definite.
❌ I will definatly attend.
✅ I will definitely attend.
Definately
Definately is also incorrect.
This form is particularly easy to produce because the pronunciation can make the spelling feel natural.
❌ She definately agreed.
✅ She definitely agreed.
The correct spelling uses i, not a, in the relevant position:
definitely
Definitly
Definitly is another misspelling.
Here, the writer has removed the e from definite before adding -ly.
❌ We will definitly return.
✅ We will definitely return.
The correct construction remains:
definite + ly
A Simple Comparison
| Misspelling | Problem | Correct form |
| definatly | Incorrect vowel pattern and missing letter | definitely |
| definately | Uses a instead of i | definitely |
| definitly | Omits the e | definitely |
| defiantly | Different real word with a different meaning | definitely, when certainty is intended |
Merriam-Webster lists definite + -ly as the etymological basis of definitely and records its first known use in the 16th century.
Definitely in Different Types of Writing
One advantage of definitely is that it works across many varieties of English writing.
You can use it in conversation, emails, general prose, and formal writing. The main consideration is not whether the word itself is formal enough, but whether expressing strong certainty is appropriate for the claim.
Definitely in Formal Writing
Definitely is a standard English adverb and can appear in formal prose.
For example:
The evidence definitely supports the conclusion.
However, formal writing sometimes benefits from precision. If the evidence only suggests something rather than establishing it conclusively, replacing a cautious statement with definitely could overstate the evidence.
Compare:
The results suggest that the treatment was effective.
with:
The results definitely prove that the treatment was effective.
The second sentence makes a much stronger claim.
Therefore, the spelling is not the only issue. Definitely should also match the level of certainty that the writer can reasonably support.
Definitely in Academic Writing
Academic writing can use definitely, but writers should consider whether the context genuinely supports absolute certainty.
For example:
The data definitely show a relationship between the two variables.
This may be appropriate in a context where the evidence is conclusive.
In another situation, phrases such as the evidence suggests, the results indicate, or the findings support may communicate the evidence more accurately.
The important lesson is simple:
Correct spelling does not automatically make a claim accurate.
Definitely in Emails and Everyday Messages
The word is extremely natural in everyday communication.
Examples include:
I will definitely send the files tonight.
You should definitely try that restaurant.
Yes, definitely!
I definitely won’t forget.
It is also common in conversational recommendations:
You should definitely watch that movie.
Cambridge specifically notes that definitely is often used for emphasis, especially in speech.
Definitely Grammar and Word Form
Definitely is an adverb.
Its base adjective is definite.
The word family can be summarized like this:
| Word | Part of speech | Meaning |
| Definite | Adjective | Clear, certain, or fixed |
| Definitely | Adverb | Certainly; without doubt |
| Definiteness | Noun | The quality or state of being definite |
Definite
Definite describes something that is clear, fixed, or certain.
Example:
We need a definite answer by Friday.
Definitely
Definitely modifies a statement or action to indicate certainty.
Example:
We definitely need an answer by Friday.
Definiteness
Definiteness refers to the quality or state of being definite.
Example:
The definiteness of the agreement was important to both parties.
This relationship makes the spelling of definitely easier to remember.
Start with:
definite
Then add:
-ly
The result is:
definitely
Where Should Definitely Appear in a Sentence?
The position of definitely can vary depending on what you want to emphasize.
Consider:
I definitely agree.
This is a very natural placement.
You can also say:
I will definitely agree to the proposal.
Or:
She definitely knows the answer.
With auxiliary verbs, definitely often appears around the auxiliary and main verb depending on the construction:
She will definitely come.
They have definitely finished the work.
He is definitely coming.
The word can also occur with negatives:
She definitely isn’t ready.
They definitely don’t understand the problem.
The position may shift slightly in different sentence structures, but the underlying meaning remains one of certainty or strong emphasis.
Definitely vs Definatly: A Complete Comparison
The difference can be summarized in one table.
| Feature | Definitely | Definatly |
| Standard spelling | Yes | No |
| Part of speech | Adverb | — |
| Meaning | Certainly; without doubt | — |
| Derived from | Definite + -ly | — |
| Used in standard English | Yes | No |
| Appropriate in formal writing | Yes, when the meaning fits | No |
| Example | I will definitely go. | I will definatly go. |
| Correct choice | Use this | Avoid this |
The central distinction is straightforward:
Definitely is the correct spelling; definatly is a misspelling.
A Practical Case Study: Choosing the Correct Form
Imagine that you are writing an email to a colleague.
Your first draft says:
I will definatly send the report tomorrow.
The meaning is obvious, but the spelling is incorrect.
Start by identifying the base word:
definite
Then add -ly:
definite + ly
The corrected sentence becomes:
I will definitely send the report tomorrow.
Now suppose you write:
I will defiantly send the report tomorrow.
That sentence is grammatically possible, but it means something very different. It suggests that the speaker will send the report in a defiant or resistant manner.
That is probably not what the writer intended.
This example demonstrates why spelling errors involving similar-looking words can matter. Definatly is simply incorrect, while defiantly is a valid word that can accidentally change the meaning of a sentence.
Facts About the Word Definitely
Several facts help put the word into perspective:
- Definitely is an adverb.
- Its core meaning is without doubt or certainly.
- It comes from definite + -ly.
- Merriam-Webster gives 1574 as the first known use of the word.
- Cambridge classifies it as a B1-level vocabulary item in its learner dictionary.
- The word can be used as a standalone affirmative response, as in “Definitely!”
- Definatly is not an alternative standard spelling.
- Defiantly is a different word, not another spelling of definitely.
- The spelling is the same in standard American and British English.
The etymology also provides a useful spelling clue. Etymonline traces definitely to definite + -ly and traces definite ultimately to Latin definitus, related to the idea of being bounded, limited, or defined.
How to Avoid the Definitely Spelling Error
If you regularly misspell this word, use a simple three-step method.
Start With Definite
Write:
definite
Do not begin by trying to spell the whole adverb from memory.
Add -ly
Now attach the adverbial ending:
definite + ly
Check the Final Word
You should get:
definitely
If you see definatly, definately, or definitly, return to the base word definite and rebuild it.
This method is more reliable than trying to remember the pronunciation.
Frequently Asked Questions About Definitely vs Definatly
Is definitely or definatly correct?
Definitely is correct. Definatly is a misspelling and should not be used in standard English.
How do you spell definitely correctly?
The correct spelling is:
D-E-F-I-N-I-T-E-L-Y
A useful formula is:
definite + ly = definitely
Why do people spell definitely as definatly?
The mistake is likely encouraged by pronunciation and by the difficulty of remembering the internal vowels in a relatively long word. The incorrect form definatly can look plausible even though it does not follow the spelling of definite.
Is definately a correct spelling?
No. Definately is also a misspelling.
The standard spelling is:
definitely
Remember definite + ly.
What is the difference between definitely and defiantly?
Definitely means certainly or without doubt.
Defiantly means in a resistant, challenging, or disobedient manner.
For example:
She definitely agreed.
means that there is no doubt that she agreed.
She defiantly refused.
means that she refused in a resistant or challenging way.
Is definitely an adverb?
Yes. Definitely is an adverb.
It commonly modifies a statement to express certainty:
He definitely knows the answer.
Does definitely mean certainly?
Yes. Certainly is one of the closest common synonyms for definitely when the word expresses certainty. Cambridge lists certainly as a synonym in this sense.
Other context-dependent alternatives include:
- certainly
- unquestionably
- surely
- positively
- without doubt
- absolutely
These words are not interchangeable in every sentence, so the intended meaning and tone should guide the choice.
Can definitely be used by itself?
Yes.
For example:
“Are you coming?”
“Definitely!”
Here, the single word communicates strong agreement or certainty.
Is definitely acceptable in formal writing?
Yes. Definitely is a standard English word and can be used in formal writing. However, writers should use it when the context genuinely supports a strong statement of certainty.
What is an easy trick for remembering definitely?
Remember:
definite + ly = definitely
You can also remember that finite appears inside definitely:
definitely
This helps you avoid forms such as definatly and definately.
Conclusion: Definitely Is the Correct Spelling
When choosing between definitely vs definatly, there is a clear answer: definitely is the correct spelling, while definatly is incorrect.
The easiest way to remember the spelling is to connect it to the adjective definite:
definite + -ly = definitely
The word functions as an adverb and usually means certainly, without doubt, or with no uncertainty. You can use it in everyday conversations, emails, professional writing, and formal prose when the context calls for a strong expression of certainty.
Be especially careful not to confuse definitely with defiantly. The first expresses certainty; the second describes resistance or disobedience.
So, whenever you are unsure, return to the simplest rule:
Definitely is definitely the correct spelling.
For more spelling and grammar questions, continue exploring related word comparisons such as definitely vs. defiantly, successful vs. succesful, and other commonly confused English spellings.
