Every once in a while, we get questions on math.SE that seem to be trying to use the word "doubt" in a non-standard way. If you search for "doubt" (on math.SE, not here on meta), you'll find dozens of these questions. I'm wondering what exactly is meant. Often the intended meaning seems to be something like "question", but I'm not sure whether that's all there is to it. It seems that in some other languages (or perhaps in one language with many speakers) the semantic field of questions, doubts and uncertain knowledge is carved up slightly differently. Perhaps someone whose native language works that way could throw some light on this? (In my native language, German, the words are closely synonymous to their English counterparts: question/Frage, doubt/Zweifel.)
It means "question" in Indian English, though I'm not sure about all the nuances.
This is Indian English. See Vishy's Indian English Dictionary.
July 12, 2006
Vishy's Indian English Dictionary: doubt
doubt. /DOWT/. A question asking for clarification. In standard English and American, the noun doubt is uncountable and refers to a lack of complete trust in something. Doubt may be expressed as simply as doubting someone's abilities or as profoundly as someone doubting their own religious faith. Not so in India. In India, doubt can be used as a countable noun. When a school teacher goes over an intricate concept in class, she invariably leaves some students with doubts in their mind about their understanding of the material just covered. Students ask her questions to get a better understanding of the concept and each such question is called a doubt. It is entirely normal to hear a statement like "I have just one doubt, miss" or "If you have any doubts before the exam tomorrow, come see me in the staff room". The doubts in the aforementioned sentences are not as much rooted in a lack of faith as in a lack of understanding. Attentive readers would have encountered the Indian English sense of doubt a fair bit on online message boards in threads started by Indians. Titles such as "Visual Basic .NET/Oracle doubt" are not uncommon for threads on programming-related message boards. It is my understanding that this sense is mostly prevalent in southern India, but I could be wrong on this count.
In Spanish (at least in Mexico), it is perfectly common and fine to preface a question with "Tengo una duda" (literally, "I have a doubt" or "I have one doubt"). It would be entirely common to hear it just as in the example quoted in Fabian's answer. Though it would be just as likely to hear "Tengo una pregunta" ("I have one question" or "I have a question").
One of my customers is Spanish. If a native English speaker doubts what I say, it has a negative connotation, not quite that I have lied but maybe so. But for the Spanish it seems to just be not understanding what was said, not in the sense of parsing the sentence, but in the sense of not getting the meaning. It helped a lot in our relations when I realized that and stopped taking offense.
While I am not certain about how big is the set of native Hebrew speakers on this site, I figured I'd weigh in from that side of the globe.
It is perfectly fine in Hebrew to say that you are "skeptic about a proof" which translates very close (in the semantic metrics) to "having doubts about a proof".
While I can't recall hearing myself or anyone using "doubt" in such way, my memory often fails me, and it is more than likely that a native Hebrew speaker would use it that way.
Lastly, it seems that everyone but the English and the Americans use "doubt" in the non-standard way.