Cool MateCertainly vs Definitely vs Undoubtedly
When to use each in English, with meaning, register, and examples.
Certainly
Definitely
Undoubtedly
| Certainly | Definitely | Undoubtedly | |
|---|---|---|---|
| Pronunciation | 🇬🇧 /["/ˈsɜːtnli/"]/🇺🇸 /["/ˈsɜːrtnli/"]/ | 🇬🇧 /["/ˈdefɪnətli/"]/🇺🇸 /["/ˈdefɪnətli/"]/ | 🇬🇧 //ʌnˈdaʊtɪdli//🇺🇸 //ʌnˈdaʊtədli// |
| Meaning | Definitely; for sure. | For sure, without a doubt | Definitely; without a doubt. |
| Example | Without treatment, she will **almost certainly** die. | I definitely remember sending the letter. | She is undoubtedly the best candidate for the position. |
| Register | Neutral | Neutral | Formal |
| How common | Top 1,000 (very common) | Top 1,000 (very common) | Top 5,000 (fairly common) |
| CEFR level | A2 | A2 | C1 |
| Part of speech | adverb | adverb | adverb |
| Collocations | certainly agree, certainly possible, certainly not, certainly true, certainly yes | definitely agree, definitely believe, definitely know | undoubtedly true, undoubtedly clear, undoubtedly helpful |
| Antonyms | uncertainly, doubtfully | doubtfully, uncertainly | doubtfully, questionably, uncertainly |
| Common mistakes | 'Certainly' is often incorrectly used in place of 'certain' in adjectives., Learners might confuse 'certainly' with 'definitely' without noticing the subtle nuance., Some learners use 'certainly' in inappropriate contexts, such as casual greetings. | Often confused with 'defiantly' which means resisting authority., Sometimes spelled incorrectly as 'definately'. | Confused with 'undoubtably', which is incorrect., Omitting it when certainty is implied., Using it in informal contexts where 'definitely' is more suitable. |
| Usage notes | Use 'certainly' when you want to emphasize affirmation or agreement. It is more formal than 'sure' and works well in professional settings, but might feel too strong in casual conversations. | Use 'definitely' to emphasize certainty. It fits well in both spoken and written English. Avoid using it in overly formal contexts where alternatives like 'certainly' might be more suitable. | Used to emphasize certainty or strong belief; typically in formal writing or speeches, not common in casual conversation. |
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Frequently asked questions: Certainly vs Definitely vs Undoubtedly
What's the difference between Certainly, Definitely, and Undoubtedly?
Certainly: Definitely; for sure. Definitely: For sure, without a doubt Undoubtedly: Definitely; without a doubt.
Which is more formal: Certainly, Definitely, and Undoubtedly?
Undoubtedly is the most formal of these.
Which is more advanced: Certainly, Definitely, and Undoubtedly?
Undoubtedly is the highest level, at C1, on the CEFR scale.
Are Certainly, Definitely, and Undoubtedly the same CEFR level?
Certainly: A2, Definitely: A2, Undoubtedly: C1 on the CEFR scale.
What part of speech are Certainly, Definitely, and Undoubtedly?
Certainly: adverb, Definitely: adverb, Undoubtedly: adverb.
Can you show an example of each?
Certainly: Without treatment, she will **almost certainly** die. Definitely: I definitely remember sending the letter. Undoubtedly: She is undoubtedly the best candidate for the position.
Can I use Certainly, Definitely, and Undoubtedly interchangeably?
Not always. Certainly, Definitely, and Undoubtedly are related and overlap in some contexts, but they differ in register, how common they are, and usage, so swapping one for another can change the meaning or tone. Check the differences above before substituting.