From Longman Dictionary of Contemporary Englishldoce_723_zillill1 /ɪl/ ●●●S3W2 adjective1especially British EnglishILLsuffering from a disease or not feeling wellsyn sick American EnglishBridget can’t come – she’s ill.I was feeling ill that day and decided to stay at home.ill withHer husband has been ill with bladder trouble.a hospice for the terminally ill2[only before noun]HARM/BE BAD FOR bad or harmfulMany people consumed the poisoned oil without ill effects.the neglect and ill treatment of childrenHe was unable to join the army because of ill health.3 →ill at ease4 →it’s an ill wind (that blows nobody any good) →ill feeling, ill willCOLLOCATIONSverbsbe illWhat’s wrong? Are you ill?feel illI’ve been feeling ill since I woke up this morning.look illHe looked rather ill when I saw him.become ill (also get ill informal)She became ill after eating oysters.fall ill formal (=become ill)Louise fell ill while she was on holiday.be taken ill (=become ill suddenly)Henry was suddenly taken ill and had to go to the hospital.make somebody illI think it was the heat that made me ill.adverbsseriously ill (=very ill)Any seriously ill patients are usually sent to a state hospital.gravely ill formal (=extremely ill)She went to visit her grandfather, who was gravely ill.critically ill (=so ill that you might die)He got news that his mother was critically ill in hospital.terminally ill (=having a very serious illness that you will die from)He is terminally ill with cancer.chronically ill (=having a long-term illness that cannot be cured and will not get better)Chronically ill patients often find it difficult to get travel insurance.mentally ill (=having an illness of your mind)Caring for mentally ill people can be challenging.
THESAURUSill [not before noun] especially British English suffering from a disease or not feeling wellHer mother is seriously ill in hospital.I woke up feeling really ill.sick especially American EnglishillShe’s been sick with the flu.a sick childDan got sick on vacation.not very well [not before noun] ill, but not seriously illSarah’s not very well – she has a throat infection.unwell [not before noun] formal illThe singer had been unwell for some time.Symptoms include fever, aching muscles, and feeling generally unwell.poorly [not before noun] British English spoken illYour grandmother’s been very poorly lately.in a bad way [not before noun] very ill because of a seriousinjury or diseaseYou’d better call an ambulance – she looks like she’s in a bad way.be off sick British English, be out sick American English to be not at work because of an illnessTwo teachers were off sick yesterday.slightly illunder the weather (also off colour British English) [not before noun] informal slightly illSorry I haven’t called you – I’ve been a bit under the weather lately.You look a bit off colour – are you sure you’re OK?run down [not before noun] feeling slightly ill and tired all the time, for example because you have been working too hard, or not eating wellSome people take extra vitamins if they are feeling run down.often illin poor healthunhealthy and often illChopin was already in poor health when he arrived on the island. delicateweak and likely to become ill easilyShe was delicate and pale and frequently complained of headaches. He had a delicate constitution and throughout his adult life suffered from various illnesses. sickly a sickly child is often illHe was a sickly child and spent a lot of time at home on his own.His younger daughter was sickly and died when she was young.
ill• The Crolgarian police are illequipped for an investigation of this kind.• If so, it seems illmannered at best.• We were ill-prepared to camp out in the snow.• The animals had been ill-treated by their owner.illill3 noun1 →ills2[uncountable] formalHARM/BE BAD FORharm, evil, or bad luckShe did not like Matthew but she would never wish him ill.