Meaning & use
not certain
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Meanings
phrasenot comparable
having doubts or not feeling sure about something
Grammar: Used after linking verbs like 'be', 'seem', or 'feel'; often followed by 'about', 'of', or a clause with 'if' or 'whether'.
Patterns
- not certain about something
- not certain of something
- not certain if/whether ...
I'm not certain about the meeting time.
She felt not certain of her decision.
We're not certain whether they will come.
phrasenot comparable
not definitely decided or fixed; not guaranteed
Grammar: Describes plans, outcomes, or facts that are still open to change.
Patterns
- not certain that ...
- it is not certain whether ...
It's not certain that the event will happen.
The outcome of the election is still not certain.
Common combinations
- not certain about
- He's not certain about his future plans.
- not certain whether
- I'm not certain whether I can attend.
- far from certain
- The success of the project is far from certain.
- not certain of
- She was not certain of the answer.
Synonyms and how they differ
- unsure
- Means the same but is one word and slightly more informal; 'not certain' is a bit more formal.
- doubtful
- Suggests a stronger feeling of doubt; 'not certain' is more neutral.
- uncertain
- A single-word adjective that is more formal and often used in writing.
Opposites
Commonly confused: not certain or uncertain?
not certain vs uncertain
One word, more formal; 'not certain' is two words and more common in speech.
Practice
Complete the sentence: 'I'm not certain ___ the exact date.'
Choose one answer.
The correct preposition after 'not certain' is 'about' (or 'of'). 'For', 'with', and 'to' do not fit this pattern.
Make it your own
Write a sentence using “not certain”, then check it and compare it with the examples above.