衰える【おとろえる】
to become weak, to decline, to wear, to abate, to decay, to wither, to waste away
盛衰【せいすい】
rise and fall, ups and downs, welfare, vicissitudes
老衰【ろうすい】
senility, senile decay, infirmity (through age)
衰退【すいたい】
decline, degeneration, decay, waning, ebbing
衰え【おとろえ】
weakening, emaciation, decline
衰弱【すいじゃく】
weakness, debility, breakdown, prostration
古び衰える【ふるびおとろえる】
to waste away
減衰【げんすい】
attenuation, damping, decay