这首歌在广播中播放了无数次。

The song has been played ___countless times on the radio.

我支持这个观点有无数理由，我想在这里提几个重要的。

There are ___countless reasons why I support this view, I would like to mention a few of [the] important ones here.

历史上，无数文明兴衰交替。

Throughout history, ___countless civilizations have risen and fallen.