Grammar: ⚙️ Verbs in Depth: 🎭 Modals & 🌱 Non-Finite Verbs (Advanced) (B2) - Lesson 4: Passive Voice with Modals (The work must be finished.)

Grammar: Voice and Modality

B2 Lesson 4: The Passive Voice with Modals

What you will learn: By the end of this lesson, you will be able to form and use the modal passive in both the present and past to write formal rules and make deductions.

Why It Matters: Shifting Focus

The passive voice with modals is very common in formal situations like rules and announcements, where the action is more important than who does it.

👤 Active Voice (Focus on the person)

You must finish the report by 5 PM.

📄 Passive Voice (Focus on the thing)

The report must be finished by 5 PM.

The Grammar Rules 📖

Rule 1: The Present Modal Passive

The structure is always the same, regardless of the modal verb.

Subject + Modal + be + Past Participle

• Obligation (must): Helmets must be worn by all drivers.
• Advice (should): This temple is fragile. It should be respected.
• Possibility (can): More information can be found on our website.

Rule 2: The Past Modal Passive

To talk about these ideas in the past, we use a slightly different structure. This is often used for regrets or deductions about the past.

Subject + Modal + have been + Past Participle

• Past Deduction (must): The window is broken. It must have been broken last night.
• Past Regret (should): The room is still dirty. It should have been cleaned this morning.
• Past Possibility (could): The project failed. More money could have been invested.

💡 Pro Tip: Formality

The modal passive is very common in formal, written English (like signs, rules, and academic papers). In casual conversation, we often use the active voice. Choosing the right voice depends on your audience and purpose.

Practice Your Grammar 🎯

Exercise 1: Form the Modal Passive

Complete the sentences with the correct modal passive form of the verbs in brackets.

1. This important form _______ (must / sign) by the manager.
   → must be signed
2. The problem is difficult, but I believe it _______ (can / solve).
   → can be solved
3. You left your phone on the cafe table! It _______ (could / steal)!
   → could have been stolen
4. The meeting room was messy. It _______ (should / clean) after the last meeting.
   → should have been cleaned

Your Grammar Mission ⭐

Rewrite the Rules

Rewrite these active sentences in the passive voice. The new subject is given.

1. Active: You must wear shoes inside the temple.
   Passive: Shoes ________________ inside the temple.
   → Shoes must be worn inside the temple.
2. Active: Someone should clean this whiteboard.
   Passive: This whiteboard ________________.
   → This whiteboard should be cleaned.

Key Vocabulary

• Modal Verb (Noun) | កិរិយាស័ព្ទគន្លឹះ
  A special verb (like must, should, can) that changes the meaning of the main verb.
• Passive Voice (Noun) | ប្រយោគកម្មវាចក
  A sentence where the subject receives the action of the verb.
• Obligation (Noun) | កាតព្វកិច្ច
  Something that you must do because of a rule or law.
• Unattended (Adjective) | ដែលគ្មានអ្នកดูแล
  Not being watched or looked after.