She prematurely declared victory before the results were announced.

prematurely 是形容词 premature 的副词形式，由前缀 pre-（表示“在...之前”）和 mature（成熟的）组成，字面意思是“在成熟之前”。作为副词，prematurely 表示“过早地、不成熟地”，指在合适时机之前就采取行动。