###

Understanding how to use modals to express degrees of certainty, necessity, and permission is crucial for communicating effectively. Each modal verb provides different nuances. Here’s a detailed guide:

#### 1. Degrees of Certainty

Modals help us express varying levels of certainty about a situation or event. Here’s how they rank, from most certain to least certain:

##### High Certainty

– **Will**

  – **Usage:** Future events that are certain

  – **Example:** She **will** pass the exam.

– **Must**

  – **Usage:** Logical conclusion or strong belief

  – **Example:** He **must** be the new manager.

– **Should/Ought to**

  – **Usage:** Expectations that are very likely

  – **Example:** The train **should/ought to** arrive soon.

##### Medium Certainty

– **Can**

  – **Usage:** General truth or strong possibility

  – **Example:** Summers here **can** be hot.

– **May/Might/Could**

  – **Usage:** Possibility that is not certain

  – **Example:** It **may/might/could** rain tomorrow.

##### Low Certainty

– **May not/Might not**

  – **Usage:** Possibility that something won’t happen

  – **Example:** He **may not** come to the party.

– **Cannot (Can’t)**

  – **Usage:** Impossibility or strong disbelief

  – **Example:** This **cannot** be true.

### Summary Table for Degrees of Certainty

| Degree        | Modal         | Usage                         | Example                         |

|—————|—————|——————————-|———————————|

| High          | Will          | Future certainty              | She **will** pass the exam.     |

| High          | Must          | Logical conclusion            | He **must** be the new manager. |

| High          | Should/Ought to | Strong expectation          | The train **should** arrive soon. |

| Medium        | Can           | General truth, strong possibility | Summers here **can** be hot.   |

| Medium        | May/Might/Could | Less certain possibility    | It **may** rain tomorrow.       |

| Low           | May not/Might not | Uncertain non-occurrence  | He **may not** come to the party. |

| Low           | Cannot        | Impossibility                 | This **cannot** be true.        |

#### 2. Degrees of Necessity

Modals conveying necessity can communicate obligations ranging from strong necessity to advisability.

##### Strong Necessity

– **Must**

  – **Usage:** Strong obligation or necessity

  – **Example:** You **must** wear a seatbelt.

– **Have to**

  – **Usage:** External obligation or necessity

  – **Example:** I **have to** finish my homework.

##### Medium Necessity

– **Should/Ought to**

  – **Usage:** Moral obligation or advice

  – **Example:** You **should/ought to** exercise regularly.

##### Low Necessity

– **Need to**

  – **Usage:** Necessity but not as strong as “must” or “have to”

  – **Example:** You **need to** drink water.

– **Had better**

  – **Usage:** Strong advice, warning

  – **Example:** You **had better** leave now.

### Summary Table for Degrees of Necessity

| Degree        | Modal           | Usage                              | Example                                 |

|—————|—————–|————————————|—————————————–|

| Strong        | Must            | Strong obligation/necessity        | You **must** wear a seatbelt.           |

| Strong        | Have to         | External obligation/necessity      | I **have to** finish my homework.       |

| Medium        | Should/Ought to | Moral obligation/advice            | You **should/ought to** exercise.       |

| Low           | Need to         | General necessity                  | You **need to** drink water.            |

| Low           | Had better      | Strong advice/warning              | You **had better** leave now.           |

#### 3. Degrees of Permission

Modals expressing permission range from strong permission to polite requests.

##### Strong Permission

– **Can**

  – **Usage:** Granting permission, informal

  – **Example:** You **can** go out now.

##### Medium Permission

– **May**

  – **Usage:** Formal permission

  – **Example:** You **may** leave the table.

– **Might**

  – **Usage:** Less formal, tentative permission

  – **Example:** You **might** want to check before you leave.

##### Polite Permission

– **Could**

  – **Usage:** Polite permission or request

  – **Example:** **Could** I borrow your book, please?

– **Would**

  – **Usage:** Very polite permission or request

  – **Example:** **Would** you mind if I opened the window?

### Summary Table for Degrees of Permission

| Degree        | Modal         | Usage                              | Example                                 |

|—————|—————|————————————|—————————————–|

| Strong        | Can           | Informal permission                | You **can** go out now.                 |

| Medium        | May           | Formal permission                  | You **may** leave the table.            |

| Medium        | Might         | Tentative permission               | You **might** want to check.            |

| Polite        | Could         | Polite permission/request          | **Could** I borrow your book, please?   |

| Polite        | Would         | Very polite permission/request     | **Would** you mind if I opened the window? |

Understanding these nuances helps in choosing the correct modal verb to convey the right level of certainty, necessity, or permission, enhancing both clarity and politeness in communication.