If it is doubtful that something will happen, it seems unlikely to happen or you are uncertain whether it will happen.
例句
For a time it seemed doubtful that he would move at all...有一段時間他似乎根本不會搬家。It is doubtful whether Tweed, even with his fluent French, passed for one of the locals...盡管特威德能說一口流利的法語，他是否能被當作當地人還很難說。
ADJ-GRADED
懷疑的;疑惑的;拿不定主意的
If you are doubtful about something, you feel unsure or uncertain about it.
例句
I was still very doubtful about the chances for success...我對能否成功仍然深表懷疑。Why did he sound so doubtful?為什么他聽上去如此不確定？
ADJ-GRADED
(質量或價值)低劣的，不可靠
If you say that something is of doubtful quality or value, you mean that it is of low quality or value.
例句
...selling something that is overpriced or of doubtful quality...售賣漫天要價或質量低劣的東西They also seemed of very doubtful value.它們好像也沒有多大價值。
ADJ-GRADED
(通常指運動員因傷)不大可能參加（比賽）的
If a sports player is doubtful for a match or event, he or she seems unlikely to play, usually because of injury.
例句
Forsyth is doubtful for tonight's game with a badly bruised leg.福賽斯腿部嚴重擦傷，不大可能參加今晚的比賽。