What is Modality: Probability and Certainty?
Modality can also express degrees of probability and certainty about events or situations. Modal verbs like 'must,' 'should,' 'might,' 'could,' and 'may' indicate how likely or certain the speaker believes something is. This is distinct from obligation modality and is crucial for expressing nuanced beliefs and predictions.
Probability modality uses verbs like 'must' (certain), 'should' (likely), 'might' (possible), 'could' (possible), and 'may' (possible) to express degrees of certainty. Each modal indicates a different level of likelihood from high certainty to low possibility.
Step-by-step worked examples
She must be at home; her car is in the driveway.
'Must' expresses logical certainty—based on evidence, the speaker is very sure she is home. This is the highest level of probability.
He might call tomorrow.
'Might' expresses low probability or possibility—the speaker is uncertain whether he will call. It is less likely than 'should.'
They could have missed the flight.
'Could' expresses possibility—it is possible they missed the flight, but it is not confirmed. The speaker is uncertain.
Flashcards
Quick quiz
Q1.Which modal expresses highest certainty?
Q2.'She should be at the office by now.' What does 'should' mean?
Q3.Probability spectrum from high to low:
Q4.'He could be sleeping.' This expresses:
The full card deck, worked steps and AI-tutor support for “What is Modality: Probability and Certainty?” are in Notek — study by hand before your exam.
Common mistakes
Using 'must' for weak probability. — Correct: 'Must' indicates high certainty; use 'might,' 'could,' or 'may' for lower probability.
Treating 'could,' 'might,' and 'may' as identical. — Correct: All express possibility, but 'might' emphasizes lower probability; 'could' is neutral.
Confusing obligation 'should' with probability 'should.' — Correct: 'Should' in probability means 'likely based on expectation'; in obligation it means 'recommended.'
Using 'will' for logical deduction. — Correct: Use 'must' for logical certainty; 'will' is future tense, not certainty.
FAQ
What is probability modality?
It expresses how certain the speaker is about something: 'must' (certain), 'should' (likely), 'might'/'could'/'may' (possible).
What is the probability order from certain to possible?
'Must' (highest) > 'should' (likely) > 'might'/'could'/'may' (possible).
What does 'might' express?
'Might' expresses lower probability—something is possible but uncertain or unlikely.
Difference between 'must' in obligation vs. probability?
Obligation: 'required.' Probability: 'must be true' based on logic or evidence.