Cool MateCertainly vs Definitely vs Of course vs Surely
When to use each in English, with meaning, register, and examples.
Certainly
Definitely
Of course
Surely
| Certainly | Definitely | Of course | Surely | |
|---|---|---|---|---|
| Pronunciation | 🇬🇧 /["/ˈsɜːtnli/"]/🇺🇸 /["/ˈsɜːrtnli/"]/ | 🇬🇧 /["/ˈdefɪnətli/"]/🇺🇸 /["/ˈdefɪnətli/"]/ | 🇬🇧 //əv kɔːs//🇺🇸 //əv kɔrs// | 🇬🇧 /["/ˈʃʊəli//ˈʃɔːli/"]/🇺🇸 /["/ˈʃʊrli/"]/ |
| Meaning | Definitely; for sure. | For sure, without a doubt | Definitely, it's obvious. | certainly; without a doubt |
| Example | Without treatment, she will **almost certainly** die. | I definitely remember sending the letter. | Are you joining us for dinner tonight? Of course! | Surely we should do something about it? |
| Register | Neutral | Neutral | Neutral | Neutral |
| How common | Top 1,000 (very common) | Top 1,000 (very common) | Top 1,000 (very common) | Top 2,000 (common) |
| CEFR level | A2 | A2 | - | B1 |
| Part of speech | adverb | adverb | adverb | |
| Collocations | certainly agree, certainly possible, certainly not, certainly true, certainly yes | definitely agree, definitely believe, definitely know | of course not, of course yes, of course you can, of course it is | surely believe, surely know, surely must |
| Antonyms | uncertainly, doubtfully | doubtfully, uncertainly | - | doubtfully, unsure |
| 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 it in formal writing where a different expression is needed., Confusing it with other affirmations like 'certainly' or 'definitely'. | Confusing 'surely' with 'sure' — 'sure' can be an adjective., Using 'surely' as a response when a simple 'yes' would suffice., Omitting 'surely' in a sentence where it clarifies certainty. |
| 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 in informal and formal situations to affirm something obvious. Avoid in highly formal writing. | Use 'surely' to express certainty. It’s appropriate in both spoken and written contexts but is more common in formal discussions. Avoid using it in very casual conversations where simpler words like 'definitely' might fit better. |
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Frequently asked questions: Certainly vs Definitely vs Of course vs Surely
What's the difference between Certainly, Definitely, Of course, and Surely?
Certainly: Definitely; for sure. Definitely: For sure, without a doubt Of course: Definitely, it's obvious. Surely: certainly; without a doubt
Which is more advanced: Certainly, Definitely, Of course, and Surely?
Surely is the highest level, at B1, 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. Of course: Are you joining us for dinner tonight? Of course! Surely: Surely we should do something about it?
Can I use Certainly, Definitely, Of course, and Surely interchangeably?
Not always. Certainly, Definitely, Of course, and Surely 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.