I can say I'm ill or I'm sick. But what is the difference between the usage of these terms?

I've heard that one can use sick for longer-term and ill for shorter-term, but is that really correct? How are these terms different for native speakers?


8 Answers 8


While those might mean the same for the laymen, from a medical point of view, there is a difference between illness and sickness.

Medical sociology has long made the distinction between illness and sickness. Illness is the objective diagnosis that an external impartial observer is able to make based on the constellation of symptoms which the patient presents. Sickness is the social role that the patient adopts as the patient and other concerned stakeholders, in relationship with the patient, interpret the meaning of the illness.

From what I get of it, someone might see themselves as sick (with the social/role aspect of it) but not actually be ill (in a medical sense). Also, this paper might provide some useful reading.

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    That's really good information, but I wonder how closely it relates to English as actually spoken by native speakers. It probably aligns to an extent, but not entirely.
    – Ryan Haber
    Commented Jan 23, 2013 at 21:01
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    I think the distinction you make is perfectly valid, and it probably is underneath the way English is actually used. Still, I think people aren't that exact in common usage as professionals are in technical usage. That's normal. The distinction lechlucasz presents above also is valid, but not extensive enough. I have provided some idiomatic differences below, but without discussing the "why" of why we use it differently. I've just noted that we do.
    – Ryan Haber
    Commented Jan 23, 2013 at 21:04
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    I have to agree that this is specialized medical jargon, but not found in general usage. By the way, the second paper you link gives a different definition of "illness" than the source at your first link does, indicating that these terms might be in some flux even within the medical sociology community. Commented Jan 29, 2013 at 13:06
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    I find that "I am sick" occurs considerably more often than "I am ill" in the Ngram viewer, and even more so in American english. My feeling is that ill is fairly formal; the fact that "sick at home" and "ill at home" (a more formal construction in itself) have taken turns in popularity over time seems to bear this out to some degree.
    – BobRodes
    Commented Jul 4, 2013 at 18:34

From a British perspective, I'm ill is more common and general term for when you're unwell.

Being sick can refer to actually throwing up or vomiting, but it can also be used for being generally unwell.

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    Yeah, in the USA, it can also mean generally being unwell, in addition to vomiting. But we wouldn't use get ill to mean vomiting in the USA.
    – Ryan Haber
    Commented Jan 23, 2013 at 21:39
  • Also when you're using "feel" instead of "be", "sick" is much more specific. "I feel sick" means specifically "I feel nauseous" whereas "I feel ill" refers to generally feeling unwell. Commented Jan 29, 2014 at 11:44
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    This is interesting. My own (American) perspective is that "I'm ill" is not used very much at all.
    – hunter
    Commented Jun 23, 2014 at 9:23
  • He's ill or he's sick are both used in AmE. ill is a tad more formal.
    – TimR
    Commented Mar 3, 2017 at 17:56
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    We can use ngram to count frequecy of these words books.google.com/ngrams/…
    – Aliaksei
    Commented Sep 16, 2018 at 18:36

The formal range of meanings for each word is more or less the same, but they carry different connotations and usage. It may vary from region to region, but in the USA, it is fairly common to use ill for longer or more serious issues, like cancer, and sick for more immediate things, like the nausea involved in cancer treatment.

Additionally, sick is used in some idiomatic expressions where ill would not fit native sensibility.

“I am sick and tired of X,” is used to mean that somebody's patience is worn out. No native speaker would ever say ill and tired in this case. Likewise, if someone were to drink too much and vomit, one would say, “He got sick.” To get sick is so strongly connected with vomiting that you can even say, “He got sick on his shoes,” or “She got sick last night,” for instance and there will be no ambiguity among native speakers in the USA.

Likewise, to fall ill is never worded to fall sick. To us, that would be just odd.

Either word might be used to describe someone’s mental illness, such as “He is sick in the head,” or “He is mentally ill,” though the phrase “mental illness” sounds right to us, and you will probably not often hear an American, at least, use the exact phrase “mental sickness.”

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    Another metaphorical use of "sick" is in the idiom "a sick joke", meaning that it shows more than a hint of mental disturbance. Commented Jan 23, 2013 at 21:11
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    "Mental illness" is a defined medical diagnosis, e.g. depression or schizophrenia. "Mental sickness" is a somewhat poetic term for deviant/aberrant thoughts or attitudes; something like "War is the result of a sickness of the mind".
    – Martha
    Commented Jan 24, 2013 at 17:31
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    "She got sick last night" in the USA would only mean that she became ill last night. Interpreting it to specifically mean "vomited" is a British thing. Commented May 30, 2017 at 23:22

Illness refers to a medical condition.

Sickness refers to the way one feels.

Illness often makes one feel sick, so the terms are often used interchangeably in colloquial speech.

But, one can be ill without being (feeling) sick. Likewise, one might feel sick after, say, seeing blood, without being ill.


A related Australianism.

Having a day off work - for the stated reason of being too ill to attend - is known as chucking a sickie. You would never call it 'chucking an illie'.

To the question: the biggest difference is for definitions involving nausea in which case sick is used exclusively. Hence sicking up.

Additionally, the colloquial meanings (ie not strictly related to being unwell) tend to use sick. For example, sick and tired (see Ryan's ans.); fully sick (meaning really good); sick to death (worse than sick and tired); you make me sick (you are disgusting, obnoxious or offensive to my sensibilities).

  • The British version of 'chucking a sickie' is 'pulling a sickie'. An interesting directional variant! I wonder if 'pulling' here is linked with 'pulling the wool over someone's eyes' (meaning 'to deceive')?
    – toandfro
    Commented Sep 24, 2013 at 22:54
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    @toandfro Or 'pulling it off'? Successfully taking the sick day? Commented Jan 29, 2014 at 11:50

In Indian context both can be used interchangeably. But there is a subtle difference between the two. Sick could be used if someone is annoyed by one's act or behavior. He'd be rather sick than feeling illness by the deeds of that person. Likewise if someone has done something wrong to me, then I'd be feeling sick.

Whereas ill means that a person has been acquired by the disease. So it might be possible that, the person might be feeling sick(feeling frustration due to suffering). So this is the difference between the two. But I've seen that generally people conversing in colloquial language uses the both the terms interchangeably.

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    Do you really say that the person has been acquired by the disease, and not that the person has acquired the disease?
    – TimR
    Commented Mar 3, 2017 at 17:54

A native speaker would interpret them as having the same meaning.

You could say "I'm ill," or you could say "I'm sick".

"I'm ill" could be classed as more formal language.

  • Additionally, at the risk of sounding like a language snob, it will be really helpful to non-native speakers - the intended target audience - if we can use correct language, spelling, etc., or make it perfectly clear when we are not, and the reason for that.
    – Ryan Haber
    Commented Jan 23, 2013 at 20:59
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    Ill (= sick) is usually used after a verb: 'I told the doctor that I felt ill.' 'His father is seriously ill in hospital.' Before a noun, use sick : 'Your father is a very sick man.' Commented Jul 8, 2015 at 8:25

Being ill refers to both long-term and short-term diseases or ailments. It's more formal.

Being sick refers to short-term or temporary ailments, such as vomiting etc.

Besides, 'sick' is an attributive adjective, i.e., you can use 'sick' before a noun; but you cannot use 'ill' before a noun in the sense of ailment.

"The boy felt sick and went home after the third period."

"I've been ill with the flu for the past few days."

"The mother took care of her sick child."

ILL has some other meanings :

(1) evil/wicked : Ill men conspire against him.

(2) morally reprehensible : It's ill to keep a lady waiting.

(3) harsh/cruel : I dislike his ill manners.

SICK has the following meanings :

(1) in bad taste : That is a sick joke.

(2) tired of / annoyed with : I am sick of that song.

(3) in poor condition : My job prospects are pretty sick.

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