Express Uncertainty in English: Practise Might, Probably and I Am Not Sure
Practise uncertainty in English with might, probably and I’m not sure. Match your wording to what you actually know and update it when the evidence changes.
Choose the uncertainty signal after you decide what you actually know.
“He’ll definitely be here at six.” Maybe. But if all you know is that he left work twenty minutes ago, your grammar has quietly upgraded a guess into a fact.
Don’t borrow certainty you don’t have: Fact → Confidence → Signal → Update.
Start with the evidence, not the uncertainty word
British Council LearnEnglish teaches that English can express different degrees of certainty with modal verbs, adverbs and other expressions. That does not mean every expression has a fixed percentage. The useful question is simpler: what do you actually know?
- If you only see a real possibility, language such as might, may or could can fit.
- If you expect an outcome but still leave room for it to be wrong, probably can fit.
- If the important message is your own lack of certainty, say I’m not sure and name what you are unsure about.
Might: keep a possibility open
British Council grammar guidance explains that may, might and could can express a specific possibility that is possible but not certain.
Original practice example
I might be late.
The speaker presents lateness as a real possibility without claiming that it will definitely happen.
Useful when traffic, another appointment or another unresolved factor could delay you.
Stance: possible, not certain.
Name one thing that could realistically happen today but is not decided.
Explore more language-learning guides in Media-Based Language Learning.
Probably: show the direction of your expectation
Cambridge Grammar lists probably among adverbs used to express degrees of certainty. In everyday use, it can show that you expect an outcome while still leaving room for a different result.
Original practice example
She’ll probably arrive around six.
The speaker expects an arrival around six but does not present the time as guaranteed.
Useful when you have a reasonable basis for an expectation but not a confirmed fact.
Stance: expected, still uncertain.
Take one reasonable expectation and say it with probably without adding a fake certainty percentage.
I’m not sure: name the uncertainty directly
Sometimes the most useful information is not your guess. It is the fact that you do not know enough yet.
Original practice example
I’m not sure whether this is the right entrance.
The speaker clearly identifies the uncertain point: whether this entrance is correct.
Useful when you need to state uncertainty about a place, fact, memory, time or decision.
Stance: explicit speaker uncertainty.
Finish “I’m not sure whether…” with one real uncertainty from today.
These forms are tools, not a percentage ladder
Cambridge Grammar notes that could, may and might express possibility and that speakers do not universally agree on which one expresses more or less certainty. So avoid charts that pretend one modal always equals one exact confidence level.
Original practice example
He might be at home, but I’m not sure.
The modal presents one possible explanation; the second phrase makes the speaker’s uncertainty explicit. The forms can work together rather than occupying fixed rungs on a ladder.
Useful when you can suggest one possibility but want to make clear that you do not know.
Stance: possibility + explicit uncertainty.
Name one possible explanation, then add an honest uncertainty phrase if the evidence is weak.
Confidence Switchboard: change the sentence when the evidence changes
Write your sentence before opening each model. The point is not to find one “correct” uncertainty word forever. The point is to match the current evidence.
Round 1: a package
Evidence A: The tracking page only says the parcel is in your city.
See one possible sentence
“It might arrive today.”
New evidence: The tracking page now says it is out for delivery.
See one possible update
“It’ll probably arrive today.”
The evidence now supports a stronger expectation, but the delivery is still not a completed fact.
Round 2: a friend
Evidence A: Your friend texted, “I’m leaving work now.” You do not know the traffic.
See one possible sentence
“She’ll probably be here around seven.”
New evidence: She sends another message saying there is a major delay and she does not know the arrival time.
See one possible update
“I’m not sure when she’ll get here.”
Round 3: missing keys
Evidence A: You remember wearing your coat when you last used the keys.
See one possible sentence
“They might be in my coat pocket.”
New evidence: You check the coat and the keys are not there.
See one possible update
“I’m not sure where they are now.”
Round 4: meeting finish time
Evidence: The meeting usually takes an hour, but today there are extra agenda items.
See one possible sentence
“It’ll probably finish after four, but I’m not sure exactly when.”
Correction lab: uncertainty grammar without fake precision
“I might to be late.”
Classification: wrong in standard English.
What a listener will probably understand: lateness is possible.
Likely learner intent: express a possibility with might.
Natural alternative: “I might be late.”
Context note: might takes the base verb without to.
“I am probably be late.”
Classification: wrong in standard English for the intended meaning.
What a listener will probably understand: the speaker expects to be late.
Likely learner intent: express a probable future outcome.
Natural alternative: “I’ll probably be late.” or “I’m probably going to be late.”
Context note: probably is an adverb; the surrounding verb structure still needs to be complete.
“I’m not sure is he coming.”
Classification: wrong in standard English for this embedded-question structure.
What a listener will probably understand: the speaker is uncertain whether he is coming.
Likely learner intent: state uncertainty about another person’s plan.
Natural alternative: “I’m not sure if he’s coming.” or “I’m not sure whether he’s coming.”
Context note: after I’m not sure, an embedded yes/no question normally uses statement word order.
“Might is always less certain than may.”
Classification: not a safe universal rule.
What a learner may infer: the two modals have fixed positions on a certainty scale.
Likely learner intent: build a simple ranking to choose between them.
Natural alternative: treat may, might and could as possibility forms whose exact force depends on context.
Context note: Cambridge explicitly notes disagreement among native speakers about which of these forms expresses more or less certainty.
The confidence rewrite
Find one sentence you said today that sounded certain. Ask what evidence you actually had. If the evidence was weaker than the sentence, rewrite it with a possibility, probable expectation or explicit not-sure phrase.
Don’t borrow certainty you don’t have
Uncertainty is not failed English. It is useful information. Separate the fact from the guess, decide how strongly you lean, choose language that matches, and update the sentence when the evidence changes.