1To become weaker or to abate (in strength, intensity, or force); used intransitively for things like weather, feelings, or pain subsiding.
台風の勢力が夜になって弱まった。
The typhoon's strength weakened during the night.
朝になると風が弱まって、外に出やすくなった。
By morning the wind had calmed, making it easier to go outside.
薬を飲んだら、頭痛が少し弱まった。
After taking the medicine, the headache eased a bit.