未來的義務
型態
當我們在談有關未來的義務時，我們可以用兩個要素來構成正式的句型：
依主詞來對 Be 動詞做現在式的詞形變化 + 主要動詞的不定詞
未來的義務，以 to travel 為例
| 肯定句 | 否定句 | 疑問句 | 否定疑問句 |
|---|---|---|---|
| I am to travel. | I am not to travel. | Am I to travel? | Am I not to travel? |
| You are to travel. | You are not to travel. | Are you to travel? | Aren't you to travel? |
| He is to travel. | He is not to travel. | Is he to travel? | Isn't he to travel? |
| It is to travel. | It is not to travel. | Is it to travel? | Isn't it to travel? |
| We are to travel. | We are not to travel. | Are we to travel? | Aren't we to travel? |
| They are to travel. | They are not to travel. | Are they to travel? | Aren't they to travel? |
作用
在英語的書寫中，我們可以用此句型來論及未來要履行的義務或要求。它的意思跟 must 相似，但有「某事已為我們安排或籌劃」之意，一般並不會用在英語的口語上。
舉例
- You are to leave this room at once, and you are to travel by train to London.
- In London you are to pick up your ticket from Mr Smith, and you are to fly to your destination alone.
- When you arrive, you are to meet our agent, Mr X, who will give you further information.
- You are to destroy this message now.