After decades apart, their emotional reunion was filled with joy and nostalgia.

reunion 是由前缀 re-（表示"再次"）和 union（"联合、结合"）组成的复合名词，字面意思是"再次联合"。这个词特指亲友或团体成员在分离后的重新相聚，常带有强烈的情感色彩。