Modal Verbs of Probability and Past Speculation

Modal Verbs of Probability

These structures are used after an infinitive verb to express certainty.

• Must (90%): Used for strong probability.
  Example: He must be at home now. (Debe estar en casa ahora.)
• Might / May / Could (70%): Used for possibility.
  Example: She might be late. (Puede que llegue tarde.)
• Can’t (Impossible): Used when something is impossible.
  Example: He can’t be the thief! (¡No puede ser el ladrón!)

Speculation in the Past

These structures are used after the auxiliary 'have' to talk about past events.

Might, May, and Could

Use Might / May / Could + have + past participle to talk about something possible or to form hypotheses.

• Example: Slaves must have built the pyramids.
• Negative (Something possible that didn’t happen): Use May / Might.
• Negative (To dismiss possibilities): Use Can / Could.

Must for Logical Conclusions

Use Must + have + past participle for logical deductions.

• Logical conclusion: People believe pyramids must have been built as tombs for pharaohs.
• Almost certain: I must have left my coat at your house; I remember I took it off there.

Should and Shouldn’t

Use these when we believe someone did or didn’t do something and we think it was an error.

• Example: You shouldn’t have joined the rowing club; you are afraid of water.
• Example: You should have looked in different shops before you bought it.

The Third Conditional

The third conditional is used to speculate about impossible situations or hypothetical situations in the past.

Structure: If + past perfect (had + -ed/3rd form), would have + past participle

• Affirmative: If I had gone with them, I would have missed my parents.
• Negative: If my friend hadn't invited me to his house, I wouldn't have had this amazing experience.
• Interrogative: If I had travelled with them, what would it have been like?

Vocabulary: Ancient Monuments

• Archaeologist: Arqueólogo
• Path: Sendero/camino
• Build: Construir
• Pharaoh: Faraón
• Circular: Circular
• Primitive: Primitivo
• Construction: Construcción
• Pyramid: Pirámide
• Drawing: Dibujo
• Stone: Piedra
• Egypt: Egipto
• Stonehenge: Monumento de piedras (England)
• Structure: Estructura
• Geometric: Geométrico
• Tomb: Tumba
• Huge: Enorme
• Tonnes: Toneladas

UFOs and Aliens

• Alien: Extraterrestre
• Fake: Falso
• Being: Ser
• Footage: Cortometraje/metraje
• Clue: Pista
• Military: Militar
• Conspiracy theory: Teoría de la conspiración
• Newspaper reports: Reportajes de periódicos
• Controversy: Controversia
• Spaceship: Nave espacial
• Crash: Choque/accidente
• Truth: Verdad
• UFO: OVNI
• Debris: Escombros
• Documentary: Documental

Mysteries and Phenomena

• Pattern: Patrón
• Crop circles: Círculos en los cultivos
• Mysterious: Misterioso
• Evidence: Evidencia
• Phenomenon / Phenomena: Fenómeno/os
• Theory: Teoría
• Fact: Hecho
• Prove: Demostrar/probar
• Hoax: Engaño/farsa