questionable, doubtful, ambiguous, uncertain

形容詞 doubtful:

1. open to doubt or suspicion- Karen Horney
   同義詞：dubious, dubitable, in question
2. fraught with uncertainty or doubt
   同義詞：dubious
3. unsettled in mind or opinion
   同義詞：tentative

1. The ethics of his decision are doubtful.
   他的這一決定是否合乎道德規(guī)范值得懷疑。
2. It is doubtful whether he can read my fortune or not.
   他能否算出我的運(yùn)氣還是個疑問。
3. I am doubtful about the propriety of granting such a request.
   我懷疑答應(yīng)這項(xiàng)要求是否合適。
4. A doubtful claim; doubtful prospects.
   令人懷疑的索賠案; 令人可疑的前景
5. Because of a long drought, the farmers are doubtful about the prospect of a good yield.
   因?yàn)殚L時間的干旱，農(nóng)民們對于好收成的前景是懷疑的。

doubt.ful

adj.（形容詞）
Subject to or causing doubt:
可疑的，令人懷疑的：
例句：
a doubtful claim; doubtful prospects.
令人懷疑的索賠案；令人可疑的前景

Experiencing or showing doubt:
疑惑的，懷疑的：
例句：
Doubtful that the cord would hold, we strengthened it.
繩索恐怕不能支撐，讓我們使它堅(jiān)固一點(diǎn)

Of uncertain outcome; undecided.
不能確定的：未決的；未定的
Raising doubts as to legitimacy, honesty, or respectability; suspicious:
令人質(zhì)疑的：合法性、誠實(shí)性或名聲有問題的；不可靠的：
例句：
the candidate`s doubtful past.See Usage Note at doubt
這位候選人過去名聲令人質(zhì)疑參見 doubt

【引伸】
doubt.fully
adv.（副詞）
doubt.fulness
n.（名詞）
<參考詞匯><同義詞>doubtful,dubious,questionableThese adjectives express a degree of uncertainty or reservation about someone or something.
這些形容詞都表示不確定的程度或?qū)δ橙?、某事的異議。
Doubtful suggests pronounced lack of certainty:
Doubtful 表示明顯的不確定性：
例句：
It is doubtful whether she will be admitted to graduate school.
她能否考上研究生很可疑。

例句：
He is an author of doubtful reputation.
他是一位名聲不太好的作家。

Dubious expresses uncertainty less directly and less forcefully;often it suggests hesitancy, suspicion, or mistrust:
Dubious 表示的不確定性不那么直接和不那么強(qiáng)，通常它含有猶豫不決、猜疑、不信任的意思：
例句：
dubious about agreeing to go;
遲疑不決到底同意還是不同意去；

例句：
a painting of dubious value.
價值沒法斷定的畫。

Questionable can mean merely open to question (
Questionable 意思是.值得疑問的.：（
例句：
Whether this is true is questionable); often, however, it implies dubious morality, respectability, or propriety:
這是不是真的倒成問題）； 然而，它通常暗指道德、名聲或行為等的有問題：

例句：
questionable dealings;
不正派的行為；

例句：
a questionable stockbroker.
不正當(dāng)?shù)墓善苯?jīng)紀(jì)人