Modal Deduction
- Not: Make logical guesses with must (sure), can't (impossible), might/may (possible).
- Not: Separate deduction (tahmin) from obligation (zorunluluk).
- TR: Kanita dayali tahmin yurutmek (olmalidir, olamaz, olabilir).
Start the 8-question quizAdapts to your answers · every miss links back to the rule
Rule in 60 secondsThe one pattern to memorise.
- Present deduction: must/can't/might/may + base verb.
- Past deduction: must/can't/might have + V3.
- TR: Eminsen must, imkansizsa can't, supheliysen might/may.
FormsHow it looks in sentences.
| Certainty | Present | Past |
|---|---|---|
| 95% sure (yes) | He must be tired. | He must have been tired. |
| 95% sure (no) | She can't be at home. | She can't have left yet. |
| 50% possible | They might be late. | They might have missed the bus. |
| 50% possible | It may rain. | It may have rained. |
- must (deduction) ≠ must (obligation): "He must be rich" (tahmin) vs "I must wear uniform" (zorunluluk).
- TR: Cumle kanita dayaniyorsa tahmin, kurala dayaniyorsa zorunluluk.
- Not: Negative deduction uses can't, not mustn't: "He can't be serious."
- TR: Tahminde olumsuzluk can't ile kurulur.
- Örnek:
must + V (eminim) / can't + V (imkansiz) / might + V (belki) - Örnek:
She MUST BE at work — her car is here. - Örnek:
He CAN'T BE 40 — he looks 25. - Örnek:
They MIGHT BE lost — let's call them. - Örnek:
PAST: She MUST HAVE FORGOTTEN. / They CAN'T HAVE ARRIVED yet.
3 classic trapsWhere Turkish speakers slip.
- Tuzak 1 — Mustn't for deduction: ❌
He mustn't be at home. (means "forbidden", not "impossible")→ ✅He can't be at home. - TR: Tahminde olumsuzluk can't, yasaklamada mustn't.
- Tuzak 2 — Must vs have to confusion:
- Deduction: She must be tired. (I guess so)
- Obligation: She has to work late. (her boss says so)
- TR: have to ile tahmin yapilmaz.
- Tuzak 3 — Forgetting have + V3 for past guesses: ❌
He must finished early.→ ✅He must have finished early. - TR: Gecmis tahmini icin have + V3 sart.
10 example sentencesRead aloud, twice.
- She must be tired after that long trip. — O uzun yolculuktan sonra yorgun olmali.
- He can't be at home; the lights are off. — Evde olamaz, isiklar kapali.
- They might be stuck in traffic. — Trafige takilmis olabilirler.
- It may rain this evening. — Bu aksam yagmur yagabilir.
- You must have been shocked by the news. — Haber seni soke etmis olmali.
- She can't have said that; she is too polite. — Oyle demis olamaz, cok kibardir.
- He might have forgotten the meeting. — Toplantiyi unutmus olabilir.
- This must be the right address. — Burası dogru adres olmali.
- They can't have arrived yet; the flight just landed. — Henuz varmis olamazlar, ucak yeni indi.
- You must try this dessert; it's amazing. — Bu tatliyi denemelisin, muhtesem. (tavsiye/zorunluluk tonu)
Quick checkCover the answers, say yours first.
- Soru 1: Lights are off → He ___ be at home. (must/can't) → can't.
- Soru 2: She has three cars → She ___ be rich. → must.
- Soru 3: Fix: "He mustn't be serious." (deduction) → He can't be serious.
- Soru 4: Maybe 50%: They ___ be late. → might/may.
- Soru 5: Past guess: She ___ have forgotten. (must) → must.
- Soru 6: Impossible past: They ___ have arrived yet. → can't.
- Soru 7: Deduction or obligation? "I must wear a tie at work." → obligation.
- Soru 8: Fix: "He must finished." → He must have finished.