Refers to the alternating rise and fall of fortunes, especially in life, career, or nature. Often used in the set phrase 栄枯盛衰.
人生には栄枯盛衰がつきものだ。
Life is full of ups and downs.
彼は会社の栄枯を身をもって経験した。
He experienced the vicissitudes of the company firsthand.
浮き沈み is the everyday, colloquial word for ups and downs in fortune, whereas 栄枯 is literary and used in formal or written contexts.
ups and downs of life; vicissitudes of fortune
Compound of 栄 (ei, 'glory, prosperity') and 枯 (ko, 'wither, decline'). The pairing of opposites is a common pattern in classical Chinese-derived compounds.