The decline or deterioration of quality, performance, or material over time; commonly used for aging of equipment or materials.
長期間放置したワイン瓶は風味が劣化することがある。
Wine bottles left for a long time can sometimes lose their flavor.
電池は繰り返し充放電をすると劣化して容量が減る。
Batteries deteriorate with repeated charging and discharging, reducing their capacity.
素材の劣化を防ぐために適切な保管が必要だ。
Proper storage is necessary to prevent material deterioration.
Colloquially, visible aging or becoming less attractive—used informally about people or things losing appeal over time.
彼は最近写真を見て、自分の顔が劣化したと言っていた（冗談めかして）。
He joked recently after seeing a photo that his face had 'deteriorated'.
古い建物は外観が劣化しているが、修復すれば魅力が戻ることも多い。
Old buildings may look worn, but restoring them can often bring back their charm.