With hard work and dedication, their ambitious project gradually became a reality.

became 是动词 become 的过去式，意思是"变成、成为"。 a 是不定冠词，表示"一个"。 reality 是名词，来自形容词 real（真实的），意思是"现实、真实存在的事物"。 became a reality 表示"成为现实"，指从计划或设想转变为实际存在的事物。