sure

sure — adjective

1. feeling certain about something, without any doubt or uncertainty in your mind

1.adjectiveA2
Definition

feeling certain about something, without any doubt or uncertainty in your mind

Example

Ada was sure she had turned off the stove before leaving the house.

be sure + that-clause for certainty about an action

The tour guide seemed sure of the path even in the thick fog.

be sure of + noun phrase for confidence in knowledge

Common collocations
  • not sure about
  • sure of
  • feel sure
  • seem sure
Synonyms
  • certain

    more formal than 'sure'; 'certain' sounds more objective

  • confident

    emphasises belief in one's own ability rather than factual certainty

  • positive

    stronger emphasis; 'I'm positive' means no doubt at all

Antonyms
  • unsure

    direct opposite; uncertain or doubtful

  • doubtful

    suggests suspicion that something is not true or right

Grammar Patterns

be sure + of/about + noun phrase

be sure + (that) + clause

Usage Note

Often used in questions and negative statements to express hesitation or seek confirmation. The that-clause can omit 'that' in informal speech.

Common Mistakes

I am surely that the door is locked.
I am sure that the door is locked.
'sure' is an adjective here, not an adverb; use 'sure' after 'be'.

2. used to say that a fact or situation is definitely true, with no possibility of

2.adjectiveB1
Definition

used to say that a fact or situation is definitely true, with no possibility of being wrong

Example

One thing is sure — the price of fresh eggs will go up again.

one thing is sure — [statement] for emphasizing an obvious fact

It is sure to rain later this afternoon, so please bring an umbrella.

be sure to + verb for inevitable events

Common collocations
  • sure to
  • one thing is sure
  • that much is sure
  • as sure as
Synonyms
  • certain

    interchangeable in impersonal constructions ('it is certain that...')

  • inevitable

    stronger; suggests something cannot be avoided, not just predicted

  • bound

    follows the same pattern ('bound to happen') but slightly less formal

Antonyms

Grammar Patterns

one thing is sure: [statement]

It is sure to + verb

Usage Note

This sense typically uses an impersonal subject ('it', 'one thing', 'that much') rather than a person. 'It is sure to…' expresses strong prediction about future events.

Common Mistakes

He is sure to be the new manager by next month.' (ambiguous — could mean 'confident' or 'destined')
It is sure that he will be the new manager.' or 'He is certain to become the new manager.
to avoid confusion between sense 1 (confident) and sense 2 (destined), rephrase with 'it' or 'certain'.

3. having more confidence than is wise, so that you may become careless or come acr

3.adjectiveB2
Definition

having more confidence than is wise, so that you may become careless or come across as arrogant

Example

Dario was sure he could finish the marathon in under three hours.

be sure + that-clause with overconfident nuance

The young player was too sure of his talent and stopped practising regularly.

too sure of + noun phrase highlighting overconfidence

Common collocations
  • too sure
  • sure of yourself
  • sure of victory
Synonyms
  • overconfident

    more direct and unambiguous negative meaning

  • cocky

    informal; suggests annoying arrogance

Antonyms
  • humble

    modest about one's own abilities

  • cautious

    careful and not taking unnecessary risks

Grammar Patterns

too sure of/about + noun phrase

be sure + that-clause (overconfidently)

Usage Note

This sense carries a negative or critical tone. It contrasts with sense 1 by implying that the speaker thinks the person's confidence is not justified. Often used with 'too'.

Common Mistakes

❌ 'She is too sure of passing without studying, but she failed.' (correct but the pattern can be confused with sense 1) — Use 'overconfident' directly for clarity: 'She was overconfident about passing and failed.'

4. confident that a particular belief or opinion about someone or something is corr

4.adjectiveA2
Definition

confident that a particular belief or opinion about someone or something is correct

Example

Abigail is sure that her son will do very well in the entrance exam.

be sure + that-clause for expressing a firm belief

The mechanic was sure of the problem after listening to the strange engine noise.

Common collocations
  • sure that
  • sure of
  • quite sure
  • pretty sure
Synonyms
  • convinced

    slightly stronger; suggests someone has persuaded you or you have reasoned it out

  • certain

    more formal and objective than 'sure'

Antonyms
  • unsure

    not certain about a belief or opinion

Grammar Patterns

be sure + (that) + clause

be sure of + noun phrase

Usage Note

Distinguish from sense 1: sense 4 is specifically about holding a firm belief or opinion about a situation or person, not about factual knowledge. Frequently used with 'that' to introduce the belief.

Common Mistakes

I'm sure to pass the exam.' (this means 'I am destined to pass,' not 'I believe I will pass.')
I'm sure I will pass the exam.
use a 'that'-clause after 'sure' for beliefs, not 'sure to'.

5. someone or something you can depend on because they are honest, work correctly,

5.adjectiveB1
Definition

someone or something you can depend on because they are honest, work correctly, or do what is needed

Example

Salma is a sure friend who will never let you down in difficult times.

sure + noun — attributive use for reliable people or things

The carpenter's sure hand is visible in every joint of the handmade cabinet.

collocation: sure hand — skilled and reliable touch

Common collocations
  • sure friend
  • sure sign
  • sure way
  • sure reputation
  • sure method
Synonyms
  • reliable

    most direct synonym; works in both attributive and predicate positions

  • dependable

    emphasises consistency over time

  • trustworthy

    focuses on honesty and integrity in people

Antonyms
  • unreliable

    cannot be trusted or depended on

  • risky

    involves danger of failure rather than lack of trust

Grammar Patterns

sure + noun (e.g., sure friend, sure sign, sure way)

Usage Note

In this sense 'sure' is almost always used directly before the noun it modifies (attributive position). You cannot say 'the friend is sure' to mean reliable — that would mean the friend feels certain.

Common Mistakes

This knife is sure.' (sounds like the knife feels certain)
This is a sure knife.' or 'This knife is reliable.
'sure' as 'trustworthy' can only go before a noun, not after 'be'.

6. so obviously going to happen or be done that there is no real question about it

6.adjectiveB1
Definition

so obviously going to happen or be done that there is no real question about it

Example

If you keep practising every single day, improvement is sure to come.

be sure to + verb for inevitable outcome

The new science fiction film is sure to be a big hit with young audiences.

Common collocations
  • sure to happen
  • sure to win
  • sure to be
  • sure to come
Synonyms
  • bound to

    identical in meaning and structure

  • destined to

    suggests fate or a predetermined outcome

  • guaranteed to

    strong emphasis; sometimes used in marketing or promises

Antonyms

Grammar Patterns

be sure to + infinitive

Usage Note

Only sense that uses 'sure to + infinitive' to mean 'certain to happen.' Distinguish this from sense 4 ('I am sure I will…'), where 'sure' is followed by a clause, not 'to + infinitive.'

Common Mistakes

I am sure to finish the report by Friday.' (ambiguous — could mean 'I confidently predict' or 'I am destined to')
For the 'bound to' meaning: 'The report is sure to be finished by Friday.
use with an inanimate subject to avoid ambiguity.

7. to check something or take action so that a particular thing happens, is true, o

7.adjectiveA2
Definition

to check something or take action so that a particular thing happens, is true, or gets done correctly

Example

Ada made sure the front door was locked before she went to bed.

make sure + that-clause for checking an action was done

Please make sure to bring your passport to the airport check-in counter tomorrow.

make sure to + verb for reminding someone

Common collocations
  • make sure that
  • make sure to
  • just to make sure
Synonyms
  • ensure

    more formal; used in written and official language

  • verify

    specifically means to check and confirm, not to take action

  • confirm

    to check that something is true or has been done

Grammar Patterns

make sure + (that) + clause

make sure to + infinitive

Usage Note

This is always part of the fixed phrase 'make sure' (or 'be sure to' in imperatives). The 'that' after 'make sure' can be dropped in informal speech. For instructions, 'make sure to…' and 'be sure to…' are interchangeable.

Common Mistakes

I made sure the door.' (missing a clause)
I made sure the door was locked.' or 'I made sure to lock the door.
'make sure' must be followed by a clause or 'to + infinitive', not a direct object.

8. having a deep, thorough, and reliable understanding or skill in a particular are

8.adjectiveC1
Definition

having a deep, thorough, and reliable understanding or skill in a particular area

Example

The professor has a sure grasp of ancient Greek philosophy and ethics.

sure grasp of [subject] — academic collocation

After years of study, Ife has a sure understanding of traditional Chinese medicine.

Common collocations
  • sure grasp
  • sure understanding
  • sure knowledge
  • sure command
Synonyms
  • thorough

    emphasises completeness rather than reliability

  • solid

    informal; describes knowledge that is well-grounded

  • masterful

    suggests expert-level skill or understanding

Antonyms
  • shaky

    not firm or reliable; uncertain

Grammar Patterns

sure + knowledge/understanding/grasp/command

Usage Note

Only used before abstract nouns related to knowledge or skill (grasp, knowledge, understanding, command, instinct). Never used before concrete nouns in this sense. Primarily found in formal and academic writing.

Common Mistakes

She has a sure English.' (incorrect — 'sure' cannot modify 'English' directly)
She has a sure command of English.
use one of the standard collocations: grasp, knowledge, understanding, command.
Idioms

for sure

idiom

used to emphasise that something is definitely true or will definitely happen; also used as an enthusiastic way of agreeing with someone

Soraya will be at the party tonight for sure — she never misses a celebration.

"That was the best meal I have had all year!" — "For sure!"

sure enough

idiom

used to say that something happened exactly as you expected or predicted it would

I thought the train would be late, and sure enough it arrived twenty minutes behind schedule.

Élise predicted it would rain by noon, and sure enough the sky turned grey at twelve o'clock.

sure thing

idiom

used as an enthusiastic way of saying yes to a request or suggestion; also used to describe something that is certain to succeed or happen

"Could you help me carry these boxes upstairs?" — "Sure thing!"

Many investors thought the new company was a sure thing, but the business failed within a year.

be sure to

idiom

used to tell someone to not forget to do something, or to give a warning or instruction

Be sure to lock the back door and check all the windows before you leave the house.

Be sure to drink plenty of water during the long hike in the hot weather.

be sure to do something

idiom

This is a way to tell someone to do something.

Be sure to lock the door before you leave.

Did you be sure to turn off the lights?

a good/safe/sure bet

idiom

Something that is very likely to happen, succeed, or be suitable.

Investing in gold is a safe bet during inflation.

That restaurant is a sure bet for a delicious meal.

make sure (of something/that…)

idiom

To do something so that you are certain about something else.

Make sure you have your passport before traveling.

Sara made sure of her reservation by calling the hotel.

sure of yourself

idiom

Feeling very confident about your own abilities or opinions.

Maya is very sure of herself during presentations.

Are you sure of yourself when you say that?

to be sure

idiom

Used to admit that something is true, often before adding a contrasting point.

The task is difficult, to be sure, but not impossible.

To be sure, Diego is talented, yet he lacks experience.

sure — adverb

Word family

Synonym discussion

Sense: adjective/1

All four words express a lack of doubt, but they differ in nuance and typical contexts. 'Sure' is the most general and conversational word — you use it in everyday speech for both facts and opinions ('I'm sure I locked the door'). 'Certain' is more formal and often suggests objective evidence ('The police are certain the suspect is guilty'), making it a better choice in writing. 'Confident' focuses on belief in one's own abilities or in a future outcome ('She is confident about passing the exam'), rather than factual certainty. 'Positive' is an emphatic, informal alternative that leaves no room for doubt ('I'm positive I saw him at the mall'). 'Convinced' implies that a process of reasoning or persuasion led to the belief ('After hearing the evidence, the jury was convinced of his innocence'). In conversation, you might say: 'I'm sure the train leaves at six, but I'm not positive about the platform number.'

certain ↗confident ↗positive ↗convinced ↗

Common collocations

Nouns

Adverbs

  • pretty sure
  • quite sure
  • absolutely sure
  • not at all sure
  • fairly sure

Phrases

Prepositions

  • sure of
  • sure about

Etymology

LatinOld FrenchEnglish

The word 'sure' entered English through Old French 'seür' meaning 'safe, secure,' which came from Latin 'securus' meaning 'without care' — a combination of 'se-' (without) and 'cura' (care). Someone who felt 'without care' was free from worry and therefore confident and certain. Over time, the meaning shifted from physical safety ('secure') to mental certainty ('sure'). The spelling in English was influenced by the Latin source, while French later developed a different spelling ('sûr').