无疑;确实;毫无疑问;的确
beyond (any) doubt
无疑;确实
in a way that shows that sth is completely certain
The research showed beyond doubt that smoking contributes to heart disease.这项研究确实表明吸烟会导致心脏病。
without / beyond doubt
毫无疑问;的确
used when you are giving your opinion and emphasizing the point that you are making
This meeting has been, without doubt, one of the most useful we have had so far.这无疑是我们迄今为止最有用的一次会议。
释义来自《牛津高阶英汉双解词典》第 9 版