Acute (medical): describing an illness or symptoms that appear suddenly and intensely; the opposite of chronic (慢性).
急性の腹痛が起こり、病院へ運ばれた。
He experienced acute abdominal pain and was taken to the hospital.
急性胃炎で入院した。
I was hospitalized for acute gastritis.
急性の症状は早めの治療が重要だ。
Early treatment is important for acute symptoms.