Definition of illness noun from the Oxford Advanced Learner's Dictionary

Oxford3000

illness

noun
ˈɪlnəs
 
; ˈɪlnəs
 
 
1 [uncountable] the state of being physically or mentally illmental illnessI missed a lot of school through illness last year.2 [countable] a type or period of illnessminor/serious illnesseschildhood illnessesHe died after a long illness.
Usage noteUsage note: IllnessesBecoming illcatch a cold/an infectious disease/the flu/(British English) flu/pneumonia/a virus/(informal) a bugget (British English) ill/(North American English) sick/a disease/AIDS/breast cancer/a cold/the flu/(British English) flu/a migrainecome down with a cold/the flu/(British English) flucontract a deadly disease/a serious illness/HIV/AIDSbe infected with a virus/a parasite/HIVdevelop cancer/diabetes/a rash/an ulcer/symptoms of hepatitishave a heart attack/a strokeprovoke/trigger/produce an allergic reactionblock/burst/rupture a blood vesseldamage/sever a nerve/an artery/a tendonBeing illfeel (British English) ill/sick/nauseous/queasybe running (British English) a temperature/(North American English) a feverhave a head cold/diabetes/heart disease/lung cancer/a headache/(British English) a high temperature/(North American English) a feversuffer from asthma/malnutrition/frequent headaches/bouts of depression/a mental disorderbe laid up with/(British English) be in bed with a cold/the flu/(British English) flu/a migrainenurse a cold/a headache/a hangoverbattle/fight cancer/depression/addiction/alcoholismTreatmentsexamine a patientdiagnose a condition/disease/disorderbe diagnosed with cancer/diabetes/schizophreniaprescribe/be given/be on/take drugs/medicine/medication/pills/painkillers/antibioticstreat somebody for cancer/depression/shockhave/undergo an examination/an operation/surgery/a kidney transplant/therapy/chemotherapy/treatment for cancerhave/be given an injection/(British English) a flu jab/(North American English) a flu shot/a blood transfusion/a scan/an X-raycure a disease/an ailment/cancer/a headache/a patientprevent the spread of disease/further outbreaks/damage to the lungsbe vaccinated against the flu/(British English) flu/the measles/(British English) measles/polio/smallpoxenhance/boost/confer/build immunity to a diseaseUsage noteUsage note: diseaseillness disorder infection condition ailment bugThese are all words for a medical problem.disease a medical problem affecting humans, animals or plants, often caused by infection:He suffers from a rare blood disease.illness a medical problem, or a period of suffering from one:She died after a long illness.disease or illness?Disease is used to talk about more severe physical medical problems, especially those that affect the organs. Illness is used to talk about both more severe and more minor medical problems, and those that affect mental health:heart/kidney/liver illness mental disease. Disease is not used about a period of illness:she died after a long diseasedisorder (rather formal) an illness that causes a part of the body to stop functioning correctly:a rare disorder of the liver. A disorder is generally not infectious. Disorder is used most frequently with words relating to mental problems, for example psychiatric, personality, mental and eating. When it is used to talk about physical problems, it is most often used with blood, bowel and kidney, and these are commonly serious, severe or rare.infection an illness that is caused by bacteria or a virus and that affects one part of the body:a throat infectioncondition a medical problem that you have for a long time because it is not possible to cure it:a heart conditionailment (rather formal) an illness that is not very serious:childhood ailmentsbug (informal) an infectious illness that is usually fairly mild:a nasty flu bugto have/suffer from a(n) disease/illness/disorder/infection/condition/ailment/bugto catch/contract/get/pick up a(n) disease/illness/infection/bugUsage noteUsage note: illnesssickness ill health troubleThese are all words for the state of being physically or mentally ill.illness the state of being physically or mentally ill.sickness illness; bad health:I recommend you get insurance against sickness and unemployment.illness or sickness?Sickness is used especially in contexts concerning work and insurance. It is commonly found with words such as pay, leave, absence and insurance. Illness has a wider range of uses and is found in more general contexts.ill health (rather formal) the state of being physically ill or having lots of health problems:She resigned because of ill health. Ill health often lasts a long period of time.trouble illness or pain:heart trouble. When trouble is used with this meaning, it is necessary to say which part of the body is affected.chronic illness/sickness/ill healthto suffer from illness/sickness/ill health/heart, etc. trouble