Ill means sick or not healthy.(adjective)
An example of an ill person is someone with pneumonia.
Ill is defined as in a bad or wrong way.(adverb)
An example of ill used as an adverb is the phrase "ill advised" which means given improper or poor advice.
The definition of an ill is an evil or a misfortune.(noun)
An example of an ill is a natural disaster like a flood.
See ill in Webster's New World College Dictionary
Origin: ME < ON illr (replacing OE yfel, evil, in many senses): prob. < Gmc *ilhila < IE base *elk-, hungry, bad > OIr elc, bad
See ill in American Heritage Dictionary 4
adjective worse worse (wûrs), worst worst (wûrst)
Origin: Middle English
Origin: , from Old Norse īllr, bad.
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