If something undoubtedly exists or is true, it is certain that it exists or is true.
近义词
without doubt , certainly
双语例句
例： Undoubtedly, political and economic factors have played their part.
毫无疑问，政治和经济因素起了作用。
例： These sort of statistics are undoubtedly alarming.
毫无疑问，这类统计数据为人们敲响了警钟。
例： It is undoubtedly true that harder times are on the way.
毫无疑问，更艰苦的日子即将到来。