Cool MateCertainly vs Definitely vs No doubt about it vs Undoubtedly
When to use each in English, with meaning, register, and examples.
Certainly
Definitely
No doubt about it
Undoubtedly
| Certainly | Definitely | No doubt about it | Undoubtedly | |
|---|---|---|---|---|
| Pronunciation | 🇬🇧 /["/ˈsɜːtnli/"]/🇺🇸 /["/ˈsɜːrtnli/"]/ | 🇬🇧 /["/ˈdefɪnətli/"]/🇺🇸 /["/ˈdefɪnətli/"]/ | 🇬🇧 //nəʊ daʊt əˈbaʊt ɪt//🇺🇸 //noʊ daʊt əˈbaʊt ɪt// | 🇬🇧 //ʌnˈdaʊtɪdli//🇺🇸 //ʌnˈdaʊtədli// |
| Meaning | Definitely; for sure. | For sure, without a doubt | It is certain. | Definitely; without a doubt. |
| Example | Without treatment, she will **almost certainly** die. | I definitely remember sending the letter. | She is, no doubt about it, the best candidate for the job. | She is undoubtedly the best candidate for the position. |
| Register | Neutral | Neutral | Neutral | Formal |
| How common | Top 1,000 (very common) | Top 1,000 (very common) | Beyond 10,000 (less 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 | have no doubt about it, leave no doubt about it, there's no doubt about it | 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'. | Using in overly formal contexts where simpler affirmatives are better., Confusing with phrases like 'no question about it' which can imply more uncertainty., Mispronouncing and rushing, making it sound unclear. | 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. | This phrase is often used in informal conversation to express certainty. It's suitable for most contexts but can be avoided in very formal writing. | 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 No doubt about it vs Undoubtedly
What's the difference between Certainly, Definitely, No doubt about it, and Undoubtedly?
Certainly: Definitely; for sure. Definitely: For sure, without a doubt No doubt about it: It is certain. Undoubtedly: Definitely; without a doubt.
Which is more formal: Certainly, Definitely, No doubt about it, and Undoubtedly?
Undoubtedly is the most formal of these.
Which is more advanced: Certainly, Definitely, No doubt about it, and Undoubtedly?
Undoubtedly is the highest level, at C1, on the CEFR scale.
Can you show an example of each?
Certainly: Without treatment, she will **almost certainly** die. Definitely: I definitely remember sending the letter. No doubt about it: She is, no doubt about it, the best candidate for the job. Undoubtedly: She is undoubtedly the best candidate for the position.
Can I use Certainly, Definitely, No doubt about it, and Undoubtedly interchangeably?
Not always. Certainly, Definitely, No doubt about it, 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.