Difference in the Use of Should, Ought to and Must

There is a lot of confusion among the students regarding the use of Should, Ought to and Must. So it is necessary to clear the difference for the correct usage. Below we are providing you this difference in their usage with the help of examples. We hope you will be benefited.

Read complete use of Modals from here.

Similar usage of Should and Ought to -

We use both to express Moral Obligation or duty -

Examples -

  1. Children should not tell a lie. or
  2. Children ought not to tell a lie.
  3. One should do one's duty. or
  4. One ought to do one's duty.

However we use Must for stronger Moral Obligation or compulsion, duty or Emphatic Advice-

Examples -

  1. You must work hard if don't want to fail this time.
  2. You must take your medicines regularly.
  3. A judge must be upright.

Both Ought to and should are used to give advice -

Check some examples -

  1. You should not drink wine daily.
  2. You ought not to drink wine daily.
  3. We should not laugh at the poor.
  4. We ought not to laugh at the poor.

Difference between Should, Ought to and Must -

Should - To express supposition in Conditional clause -

  1. If it should rain, we will not go there.
  2. If I should see him here, I will leave immediately.

Ought to - To express strong possibility -

  1. He ought to be in the school this time.
  2. We ought to win this time.
  3. He ought to be a thief.

Must - Stronger possibility than Ought to -

  1. She must be in the school this time.
  2. We must win this time.
  3. He must be a thief.

Must is used for Inevitability. We can't use should or ought to here.

Example -

Everybody must die one day.

We can's say - Everybody should or ought to die one day.

For Determination also, we use must not ought to or should.

Example -

For example - We must work hard now. ( determination )

We ought to / should work hard now. ( No determination)

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