1、作及物动词，后接 who ,what ,why ,where 等引导的宾语从句。例句：I wonder who she is.我想知道她是谁。

2、作及物动词，后接 that 引导的宾语从句,表示“感到惊奇；对……感到惊讶”,that 常可省去。例句：I wonder (that) she has won the race.我对她赢了比赛感到惊讶。

3、用作不及物动词。例句：I was just wondering.我只不过是好奇而已。