ill

The word “ill” means unwell or in poor health; sick. In plain terms, most commonly means "sick," but as an adverb/prefix it also means "badly" (ill-advised, ill-timed).

“Ill” is pronounced ihl (/ɪl/ in IPA).

Here is “ill” used in a sentence: “She stayed home from work because she felt ill.”

Words with a similar meaning to “ill” include bad, mal-, crank, crook, green about the gills and icky.

The opposite of “ill” — its antonyms — are fine, hale, healthy, in good health and well.

Depending on how it is used, “ill” can be an adjective, an adverb and a noun.

The word “ill” comes from Old Norse. From Old Norse illr, "bad, evil," related to Danish ilde and Swedish illa.

“Ill” is a very common word in modern English, usually learned at around the A2 level.

Ill and sick both mean unwell, and in most contexts they are interchangeable. British English tends to prefer "ill" for being unwell, reserving "sick" for the sense of vomiting; American English uses "sick" more broadly for any illness. "Ill" can also sound slightly more formal or more serious.

No. Besides meaning unwell, "ill" can mean bad, harmful, or hostile, as in "ill will," "ill effects," "ill-advised," or "speak ill of someone." As an adverb it means badly, as in "ill-equipped." As a noun, "ills" are troubles or problems. The unwell sense is simply the most familiar.

"Ill" is neutral to slightly formal and works in both everyday and professional writing. In British English it is the standard word for being unwell, where American English often prefers "sick." It fits comfortably in phrases like "seriously ill" or "taken ill," carrying a measured, matter-of-fact tone.

When "ill" means unwell, its opposite is "well" or "healthy" — you might say someone is "well again" after recovering. Other antonyms include "fit," "sound," and "in good health." When "ill" means harmful, as in "ill effects," the opposite shifts to "good" or "beneficial."