When a child or young animal matures, it becomes an adult. (小孩、幼崽) 发育成熟;When something matures, it reaches a state of complete development. (某物) 长成
If an action or a time when something happened is described as fateful, it is considered to have an important, and often very bad, effect on future events. 有重大影响的 (尤指产生负面结果的)