Express permission, obligation, and prohibition using MODALS

• Modal verbs


  • Used to express something that can probably certainly or possibly happen
  • Give additional information about the function of the main verb that follows it
  • Have a great variety of communicative functions
• Skills in using modals which express prohibition obligation and permission


  1. Learn

  2. Discuss
• Prohibition

  Prevent forbid stop or disallow someone from doing something
• Modals used for prohibition

  • Can't or cannot
  • Mustn't or must not
• Obligation

  Duty or commitment
• Modals used for obligation


  • Have to
  • Must
• Have to


  • The obligation comes from someone else not the speaker
  • Referring to a rule or law
• Don't have to

  • There is no obligation
  • You can do something if you want but it is not an obligation
• Must

  The obligation comes from the speaker
• Permission


  Allowing someone to do something
• Modals used for permission


  • Can
  • Could