ill / sick

Sick is the less formal word, and it usually describes a more temporary health problem – often nausea, although not always.

  • If you’re feeling sick, you might need to vomit.
  • If you get the flu, you might be sick for two weeks.
  • If a child is sick, he stays home from school that day.
  • Taking a day off from work for health reasons is called “taking a sick day.”

    Ill is the more formal word, and it usually describes a more serious, more permanent health problem, like cancer.

  • My uncle has been ill for the past five years.
  • She passed away (=died) after a long illness.
  • Someone with a mental health problem is mentally ill.
  • A disease that will definitely result in death is a terminal illness.