Modality B1 B2

Modal deduction and speculation

Judge present and future certainty with must, can't, may, might, could, and should.

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Guia visual

Modal deduction: the certainty scale

Evidence → choose the helper by certainty

IMPOSSIBLE       POSSIBLE          EXPECTED       ALMOST CERTAIN
can't            may / might /     should         must
                 could
   │                │                │              │
That can't be our taxi; the number is different.
They might be in the café.
The train should arrive soon.
The lights are on, so Ben must be home.

Shape:
person/thing + certainty helper + be / plain verb

✓ She must be tired.   ✗ She must tired.

Choose the modal by how sure the evidence makes you, then use it before be or the plain verb.

Introduction

Judging from evidence

Modal deduction and speculation help you judge what is true when you do not know for sure. You look at evidence, the situation, or normal expectations, then choose a modal to show your certainty. The lights are on, so Ben must be home. That can't be our taxi; the number is different. These sentences do not report direct facts; they report the speaker's present judgement about a present situation or a likely future result.

Core Gramática B1 Vocabulário A2 Neutral

The lights are on, so Ben must be home.

Must shows a strong logical conclusion, not obligation, because the evidence points to it.

Blocos de sentido

Lê a frase por blocos de sentido, não palavra a palavra.

The lights are on, so

evidence_frame

Gives the reason for the conclusion.

Ben must be home

strong_deduction

Shows a strong present conclusion from evidence.

Aprende como uma unidade

Negative Gramática B1 Vocabulário A2 Neutral

That can't be our taxi; the number is different.

Can't expresses a negative deduction: the speaker is sure something is not true.

Blocos de sentido

Lê a frase por blocos de sentido, não palavra a palavra.

That can't be our taxi

impossible_deduction

Shows that the speaker thinks this possibility is impossible.

Aprende como uma unidade

the number is different

evidence_frame

Gives the evidence for rejecting the idea.

Cognitive metaphor

A scale of certainty

Think of these modals as points on a certainty scale. Must is very strong: the evidence points clearly to one conclusion. Should means expected or likely because it is normal, planned, or reasonable. May, might, and could are in the middle: possible, but not claimed as certain. Can't is very strong in the opposite direction: the speaker thinks the idea is impossible. She must be the new manager. The train should arrive soon. This can't be the right key. They might be in the café.

Core Gramática B1 Vocabulário A2 Neutral

She must be the new manager.

Must be is the normal frame for a strong conclusion about identity or state.

Blocos de sentido

Lê a frase por blocos de sentido, não palavra a palavra.

She must be the new manager

strong_deduction

A strong conclusion about who she is.

Aprende como uma unidade

Core Gramática B1 Vocabulário A2 Neutral

The train should arrive soon.

Should often means the speaker expects something because it is normal, planned, or likely.

Blocos de sentido

Lê a frase por blocos de sentido, não palavra a palavra.

The train should arrive soon

expected_result

Shows an expected result, but not complete certainty.

Aprende como uma unidade

Negative Gramática B1 Vocabulário A2 Neutral

This can't be the right key.

Can't is the opposite of must for deduction: the speaker feels sure the idea is wrong.

Blocos de sentido

Lê a frase por blocos de sentido, não palavra a palavra.

This can't be the right key

impossible_deduction

Rejects the possibility as logically impossible or very unlikely.

Aprende como uma unidade

Core Gramática B1 Vocabulário A2 Neutral

They might be in the café.

Might be is useful when the speaker has a real possibility but weak evidence.

Blocos de sentido

Lê a frase por blocos de sentido, não palavra a palavra.

They might be in the café

weak_possibility

Shows a possible present location without strong certainty.

Aprende como uma unidade

Core pattern

The basic pattern

The core form is subject + modal + base verb. The modal does not add -s, -ed, or -ing, and the following verb stays in its base form. With adjectives, nouns, and places, use be after the modal. She must tired is a common mistake; She must be tired is correct. For future actions, use the same modal + base verb pattern: They may arrive early. For possible results, could is very common in speech: This could work.

Mistake Gramática B1 Vocabulário A1 Neutral

She must tired.

After a modal, English needs the base verb. With an adjective like tired, use be.

Corrected Gramática B1 Vocabulário A1 Neutral

She must be tired.

Use modal + be + adjective for deductions about states.

Blocos de sentido

Lê a frase por blocos de sentido, não palavra a palavra.

She must be tired

strong_deduction

A reusable frame for a strong conclusion about someone's state.

Aprende como uma unidade

Core Gramática B1 Vocabulário A2 Neutral

They may arrive early.

May + base verb can speculate about a future action.

Blocos de sentido

Lê a frase por blocos de sentido, não palavra a palavra.

They may arrive early

future_possibility

Shows a possible future event.

Aprende como uma unidade

Spoken Gramática B1 Vocabulário A2 Neutral

This could work.

Could often sounds natural for suggesting that something is possible.

Blocos de sentido

Lê a frase por blocos de sentido, não palavra a palavra.

This could work

possible_result

A short reusable frame for a possible solution or result.

Aprende como uma unidade

Form variations

Useful form variations

Deduction often uses be because we are judging a state, identity, place, or situation. Use modal + be + adjective, noun, or place for states and identities. Use modal + be + -ing for an action possibly happening now. Use modal + be + past participle for passive meanings. It might be raining downtown. The road may be closed. The report should be ready by noon. These patterns let you speculate about now, soon, or a future result without changing the modal form.

Core Gramática B2 Vocabulário A2 Neutral

It might be raining downtown.

Use modal + be + -ing for speculation about an action in progress.

Blocos de sentido

Lê a frase por blocos de sentido, não palavra a palavra.

It might be raining

continuous_speculation

Shows a possible action happening now.

Aprende como uma unidade

downtown

place_context

Adds the place where the situation may be happening.

Core Gramática B2 Vocabulário A2 Neutral

The road may be closed.

Use modal + be + past participle when the subject receives an action or is in a passive state.

Blocos de sentido

Lê a frase por blocos de sentido, não palavra a palavra.

The road may be closed

passive_speculation

Shows a possible passive state.

Aprende como uma unidade

Formal Gramática B1 Vocabulário A2 Formal

The report should be ready by noon.

Should be ready is common for expected completion, especially in work or service contexts.

Blocos de sentido

Lê a frase por blocos de sentido, não palavra a palavra.

The report should be ready

expected_ready_state

Shows an expected state.

Aprende como uma unidade

by noon

deadline

Gives the expected time limit.

Usage rules

Negatives and questions

Negative forms do not all mean the same thing. May not and might not mean that a negative situation is possible: the speaker is not sure. Can't means the speaker is sure the idea is not true. She may not know the address. He can't be asleep; his light is on. In questions, could is the most common neutral choice for asking about a possible explanation. Could this be a mistake? Might they need more time? Might sounds more careful or formal than could.

Negative Gramática B1 Vocabulário A2 Neutral

She may not know the address.

May not means possible non-truth, not impossibility.

Blocos de sentido

Lê a frase por blocos de sentido, não palavra a palavra.

She may not know

negative_possibility

Shows that it is possible she does not know.

Aprende como uma unidade

the address

object

Says what she may not know.

Negative Gramática B1 Vocabulário A2 Neutral

He can't be asleep; his light is on.

Can't is much stronger than may not or might not.

Blocos de sentido

Lê a frase por blocos de sentido, não palavra a palavra.

He can't be asleep

impossible_deduction

Shows the speaker is sure the idea is false.

Aprende como uma unidade

his light is on

evidence_frame

Gives the evidence for the deduction.

Question Gramática B1 Vocabulário A2 Neutral

Could this be a mistake?

Could is common and natural in questions about possible explanations.

Blocos de sentido

Lê a frase por blocos de sentido, não palavra a palavra.

Could this be a mistake

possibility_question

Asks whether something is possible.

Aprende como uma unidade

Question Gramática B2 Vocabulário A2 Formal

Might they need more time?

Might can form speculation questions, especially when the speaker is cautious.

Blocos de sentido

Lê a frase por blocos de sentido, não palavra a palavra.

Might they need more time

possibility_question

Asks about a possible need, often a little more careful or formal than could.

Aprende como uma unidade

Contrast

Deduction is not obligation

The closest confusion is must for deduction versus must for obligation. You must be cold means I conclude this from what I see or know. You must wear a coat means I am giving a rule or strong instruction. The verb pattern and situation decide the meaning. Another important contrast is can't versus mustn't. Can't can reject a possibility in deduction. Mustn't means prohibition, so it is usually a rule or warning, not a logical conclusion.

Contrast Gramática B1 Vocabulário A1 Neutral

You must be cold.

Here must is deduction because it is followed by be + adjective and fits the evidence.

Blocos de sentido

Lê a frase por blocos de sentido, não palavra a palavra.

You must be cold

deduction_not_obligation

Shows a conclusion about someone's state, not a command.

Aprende como uma unidade

Contrast Gramática B1 Vocabulário A1 Neutral

You must wear a coat.

Must can also express obligation; context and verb meaning decide the reading.

Blocos de sentido

Lê a frase por blocos de sentido, não palavra a palavra.

You must wear a coat

obligation

Shows a rule or command, not a deduction.

Aprende como uma unidade

Danger zone

Common boundaries

Do not use can for a single uncertain future guess in ordinary English. It can rain in April means rain is generally possible in April. For one specific future situation, use may, might, or could: It might rain tonight. Also remember that these modals normally describe present or future judgement in this lesson. For past deduction, English uses forms such as must have left or might have forgotten; those are a separate pattern and should not be mixed with the simple present/future frames here.

Exception Gramática B1 Vocabulário A1 Neutral

It can rain in April.

Can is natural for general possibility, but not usually for a single uncertain future event.

Blocos de sentido

Lê a frase por blocos de sentido, não palavra a palavra.

It can rain

general_possibility

Shows something that is generally possible, not a one-time guess.

Aprende como uma unidade

in April

general_time_context

Marks the sentence as a general statement about a season or period.

Summary

The practical choice

Choose the modal by asking how strong your evidence is. Use must when the evidence strongly points to yes. Use can't when the evidence strongly points to no. Use may, might, or could when something is only possible. Use should when something is expected because it is normal, planned, or likely. Keep the form simple: modal + base verb, modal + be + adjective/place/noun, modal + be + -ing, or modal + be + past participle. The modal shows your judgement, not a guaranteed fact.

Aprendizagem

Ferramentas

Explorar

Empresa & Apoio

Modal deduction and speculation

Modal deduction: the certainty scale

Judging from evidence

Blocos de sentido

Blocos de sentido

A scale of certainty

Blocos de sentido

Blocos de sentido

Blocos de sentido

Blocos de sentido

The basic pattern

Blocos de sentido

Blocos de sentido

Blocos de sentido

Useful form variations

Blocos de sentido

Blocos de sentido

Blocos de sentido

Negatives and questions

Blocos de sentido

Blocos de sentido

Blocos de sentido

Blocos de sentido

Deduction is not obligation

Blocos de sentido

Blocos de sentido

Common boundaries

Blocos de sentido

The practical choice

Aprendizagem

Ferramentas

Recursos

Empresa

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