certainly

certainly — adverb

1. used to say that something is definitely true and there is no question about it

1.adverbA2
Definition

used to say that something is definitely true and there is no question about it at all

Example

The children certainly enjoyed their trip to the farm yesterday.

certainly + verb (emphasises the statement)

Kofi certainly runs faster now than he did last spring.

subject + certainly + verb + comparative

Common collocations
  • certainly hope
  • certainly know
  • certainly look
  • certainly deserve
  • certainly remember
Synonyms
  • definitely

    more common in everyday speech, equally strong

  • undoubtedly

    more formal, often used in writing

  • absolutely

    used for emotional emphasis, common in conversation

Antonyms
  • possibly

    adds doubt instead of removing it

  • maybe

    expresses uncertainty, A1-level alternative

Grammar Patterns

certainly + verb

certainly + modal + verb

subject + certainly + verb

Usage Note

Placed directly before the main verb in a simple sentence (She certainly sings well) or after the first auxiliary verb in a verb phrase (He has certainly improved). When placed at the start of a clause, it adds extra emphasis to the whole statement.

Common Mistakes

Surely I passed the test — I got every answer right.
Certainly I passed the test
I got every answer right.' — 'Surely' expresses expectation with some doubt, while 'certainly' removes all doubt and states a fact.

2. used to give a very clear yes or no when someone asks you to do something or ask

2.adverbA2
Definition

used to give a very clear yes or no when someone asks you to do something or asks for permission

Example

"May I use your phone?" "Certainly, please go right ahead."

one-word response agreeing to a request

"Could you feed my cat while I am away?" "Certainly, I will be happy to."

Common collocations
  • certainly not
  • certainly can
  • certainly will
Synonyms
  • of course

    equally common in both UK and US English, slightly less formal

  • absolutely

    stronger emotional tone, used for enthusiastic agreement

  • sure

    informal, very common in American English

Antonyms
  • no

    direct opposite, but less polite for refusing a request

  • never

    strong refusal, more emotional than 'certainly not'

Grammar Patterns

'Certainly.' (agreeing)

'Certainly not.' (refusing)

'Certainly, [clause]'

Usage Note

This sense occurs almost exclusively in spoken conversation or direct dialogue. 'Certainly not' is a polite but firm way to say no to a request. 'Certainly' alone conveys willing agreement. Less common in American English than in British English, where 'Sure' is often preferred.

Common Mistakes

Teacher: Can you help me carry these books? Student: Yes, certainly I can help.
Teacher: Can you help me carry these books? Student: Certainly.
As a reply, 'certainly' alone is natural; adding 'yes' before it is redundant.

3. used to say that something is almost sure to happen or is very probably true

3.adverb
Definition

used to say that something is almost sure to happen or is very probably true

Example

The price of milk will certainly go up again next month.

will certainly + verb (future probability)

If no one stops him, Rohan will certainly eat the whole cake by himself.

Common collocations
  • will certainly
  • certainly be
  • certainly happen
  • certainly expect
Synonyms
  • undoubtedly

    more formal, equally strong in meaning

  • inevitably

    suggests something cannot be avoided, slightly more negative

  • surely

    expresses expectation rather than certainty, weaker

Antonyms

Grammar Patterns

will certainly + verb

certainly + present tense

be certainly + past participle

Usage Note

Unlike sense 1 (WITHOUT DOUBT), this sense does not express the speaker's own emphasis — it expresses a prediction about what is almost sure to happen. The structure 'will certainly + verb' is the most common pattern. Distinguish from sense 1: in 'I certainly hope so' (sense 1) the speaker is emphasising their feeling; in 'It will certainly rain' (sense 3) the speaker is predicting what will happen.

Common Mistakes

He certainly will be late again, I am sure of it.
He will certainly be late again, I am sure of it.
With 'will', the natural word order is 'will certainly + verb' not 'certainly will + verb', though both are sometimes used.

Word family

Synonym discussion

Sense: adverb/1

All four words express a high degree of certainty, but they differ in strength and context. 'Certainly' and 'definitely' are the most versatile; both can emphasise statements ('He certainly/definitely knows') and respond to requests ('Certainly!' / 'Definitely!'). 'Undoubtedly' is more formal and suggests that no reasonable person could disagree — it is rare in everyday conversation. 'Absolutely' carries strong emotional weight and is common in enthusiastic agreement ('Absolutely! That is the best idea'). 'Surely' is the odd one out: it expresses expectation or belief rather than certainty ('Surely you remember me?') and often implies the speaker hopes to be proven right. For a neutral, confident assertion without extra emotion, 'certainly' or 'definitely' are the safest choices.

definitely ↗undoubtedly ↗absolutely ↗surely ↗

Common collocations

Adverbs

  • almost certainly
  • quite certainly

Phrases

  • certainly not
  • most certainly

Etymology

LatinFrenchEnglish

Formed in Middle English from the adjective 'certain' (from Old French 'certain', from Latin 'certus' meaning 'sure, fixed, decided') plus the adverbial suffix '-ly'. The Latin root 'certus' comes from 'cernere' meaning 'to distinguish, decide, sift' — the original idea was of something that had been separated out and could be clearly seen, hence 'settled' or 'beyond doubt'.