word usage - I have "a doubt" about whether this phrase is acceptable English

To my (British) ear, it never sounds correct to say you have a doubt about something.

I expect that doubt to be pluralised, even if there's only one specific thing that I'm doubtful of, in one specific way, so I would always say "I have doubts about something".

Answers to this ELU question say that using doubt as a synonym for question is "Indian English". That seems to be the case in this ELL question which starts with "I have a doubt on my construction", because the OP really is saying "I have a question" (which he goes on to actually ask). Okay, it should have been a question/doubt about something, not on, but I'm not concerned with that detail here.

But in another ELL question the OP says "...there is a doubt that can I use [some construction]". In that case it's not easy to see how the word doubt can be replaced with question.

I don't have a problem with, for example, "The reason for my doubt is [some reason]", because there I interpret it as doubt=uncertainty (a state of mind, syntactically equivalent to words like happiness, agitation, sorrow, etc.). But you certainly can't "have a happiness about something". So my question is...

Is it acceptable today to use singular noun doubt in any contexts where it means something other than state of mental uncertainty? If so, what are those contexts?

Answer

Because doubt is an old word (the OED attests it from 1225) there are a number of nuances of meaning. In summary, with my numbers not OED's:

1. A subjective state of uncertainty about the truth or reality of something;



2. (plural) A feeling of uncertainty as to something;


3. The condition of being objectively uncertain;


4. A state of affairs which gives rise to uncertainty;


5. A matter or point involved in uncertainty; a difficulty (Obsolete);


6. Apprehension, dread, fear (Obsolete);


7. A thing to be dreaded; danger, risk (Obsolete).

As a singular noun, it is decidedly abstract and refers to a state of being. Thus one can be in doubt about something. As a mass noun referring to a state of being, doubt would not normally be pluralised.

When it refers to a particular feeling of uncertainty it is pluralised. Thus if one has that feeling, one has doubts. One does not "have a doubt" because the singular doubt refers to a state of being; senses 5, 6 and 7 which refer to particular things are obsolete in Standard English.

The uses which are obsolete in Standard English may have survived or been resurrected in other dialects. The ELU references say that it does occur in Indian English.