decline, weaken, deteriorate
あの事故以来、彼の健康は衰えている。
His health has been deteriorating since that accident.
彼の人気は衰えていた。
His popularity was waning.
トムの人気は衰えていた。
Tom's popularity was waning.
彼の影響力は未だ衰えていない。
His influence has not waned yet.
貿易の活動は最近衰えてきている。
Trade activity has been declining recently.