先祖的英文：
predecessor

参考例句：

The shades of my dead ancestors
我的先祖的幽魂.

The invading army violated the ancestral tombs.
侵略军亵渎了先祖的陵墓。

Trace back to１７th century,they joined in the same ancestor,Robert Spencer,second Earl of Sunderland,Knight.
追溯到１７世纪，他们的共同先祖是罗伯特·斯潘塞爵士（森德兰伯爵二世）。

They can bear in mind the hardness their ancestors experienced and carry forward the spirit of unity and struggle.
好让人们进入场地和欢快起舞时，不忘先祖创业之艰辛，发扬团结奋斗的民族精神。

predecessor是什么意思：
n. 前任，前辈；（被取代的）原有事物，前身

His predecessor was accorded an equally tumultuous welcome.
他的前任受到了同样热烈的欢迎。

The new building is more spacious than its predecessor.
这一新建筑比原先的更宽敞。

David was more politic and successful than his predecessor
大卫比他的前任精明，成就也较大。

He is a president living in the shadow of his predecessor.
他是一个在他的前任的声誉影响中过日子的总统。

She is using the same office as her predecessor.
她用的是她前任的办公室。