This is the 2209th most frequent Japanese word.
病気
Illness; disease.
Disease or illness affecting someone's health.
彼女は病気で学校を休みました。
She stayed home from school because she was ill.
Describes a specific disease that can spread to other individuals.
その病気は伝染します。
That disease is contagious.
Metaphorical usage, comparing excessive worry to feeling ill or sick.