noun
General term for illness or disease, typically excluding minor ailments like a common cold. Used in medical, everyday, and formal contexts.
彼は重い病気で入院している。
He is hospitalized with a serious illness.
病気
Hand washing is important for disease prevention.
noun
Figurative use: a personal flaw, bad habit, or moral weakness likened to an illness. Often used in self-deprecating or critical remarks.
遅刻癖は彼の病気だ。
His chronic lateness is a bad habit of his.
ギャンブルはもう治らない病気かもしれない。
Gambling might be an incurable weakness.
noun which may take the genitive case particle 'no'
crazy; insane; sick in the head
Colloquial, often used in phrases like 病気じゃない？ to suggest someone is mentally unstable or acting irrationally. Can be light-hearted or derogatory depending on context.
こんな時間に走るなんて、病気じゃない？
Going for a run at this hour? Are you crazy?
あのアイデアは病気としか思えない。
That idea seems nothing short of insane.