whether or not

• 是否对?

  Is this correct?

• 是否这样?

  Is it like this?

• 这件事他是否知道?

  Does he know about this?

• 不晓得他是否能答应。

  I don't know if he will agree or not.

• 是否请她给我们唱一段京剧?

  Shall we ask her to sing a passage of Beijing opera?