Difference between “ill” and “sick”

Ill or sick ? - Grammar

The difference between “Ill” and “Sick” in English

We often hear the words “ill” and “sick” in the English language, which refer to a state of unwellness. However, many people wonder what the difference is between them. In general, ill is a more formal word and is used to describe a general state of illness or unwellness. Sick is a less formal word and is more commonly used in casual speech. In this article, we will explore each word in detail, so that you never have any doubts about which one to use.

ill – meaning, examples of use

Ill” means to be sick, unwell, or ailing, both physically and mentally. “Ill” in English can be an adjective, adverb, or noun. Its synonyms can be words like: unwell, sick, ailing, poorly, and its antonyms are: well, healthy. Most commonly, “ill” is used as an adjective or adverb. When used as an adjective, “ill” can come before a noun: “ill health” (poor health). As an adverb, “ill” is often used with verbs: “ill advised” (poorly advised). Let’s look at its meaning in more detail.

As an adjective:

  • Means “sick” or “suffering from illness”: “He is ill” (He is sick).
  • Can indicate poor quality or harmfulness: “ill effects” (harmful effects).
  • Used to describe misfortune or unhappiness: “a series of ill fortunes” (a series of misfortunes).

As an adverb:

  • Used to describe an action performed poorly or incorrectly: “ill prepared” (poorly prepared).

As a noun:

  • Used to refer to evil or harm: “to wish someone ill” (to wish someone harm).


  • He was taken ill with food poisoning. (He fell ill with food poisoning).
  • A terminally ill patient. (A terminally ill patient).
  • She could ill afford the cost of new curtains. (She could hardly afford the cost of new curtains).
  • She has been ill for a week. (She has been sick for a week).
  • He was diagnosed with a mental illness. (He was diagnosed with a mental illness).
  • The patient looked very ill. (The patient looked very sick).

Sick – meaning and examples of use

Sick” mostly means to be physically ill, unwell, or unhealthy. “Sick” can be used as an adjective, verb, or noun. “Sick” is used as an adjective before a noun or after the verb “to be”. In American English, “sick” can be used to describe being absent from work due to illness: “She called in sick” (She reported being absent from work due to illness). Synonyms of “sick” include: ill, unwell, poorly, ailing. Antonyms are: well, healthy.

As an Adjective:

  • Means “ill” or “suffering from illness”: “She is sick” (She is ill).
  • Can indicate a feeling of nausea: “I feel sick” (I feel nauseous).
  • Used to describe intense unpleasant emotions, especially anger or disgust: “I’m sick of this situation” (I’m fed up with this situation).

As a Verb:

  • “To be sick” means “to vomit”: “He was sick after the party” (He vomited after the party).

As a Noun:

  • “The sick” refers to people who are ill: “Hospital cares for the sick” (The hospital cares for the ill).


  • “The child was sick with the flu” (The child was ill with the flu).
  • “I’m sick to my stomach” (I feel nauseous).
  • “He’s sick and tired of the constant delays” (He’s fed up with the constant delays).
  • I feel sick after eating that food. (I feel ill after eating that food).
  • The sick patient needs medical attention. (The ill patient needs medical attention).
  • She was too sick to go to school. (She was too ill to go to school).

How is it correct: ill or 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.

So in summary, “ill” encompasses a wider range of unwell states including mental health, while “sick” primarily denotes physical sickness and has a more informal connotation. Keeping this nuanced difference in meaning and level of formality in mind can help ensure the right word is chosen.

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