+0
What does a. stand for? Is it adjective?
+0
This has also been discussed recently in the thread Adjective or not?
It makes good reading.
Comments  
Hi. Formally, it's an indefinite article (a man = any man). Compare to "the", which is a definite article: the man on the corner (no other man). Now, it can be considered a preposition only in informal speech when replacing "of": sorta sad (sort of sad) or a kinda mess (a kind of mess).

(By the way, I'm new to the Forum)
Students: Are you brave enough to let our tutors analyse your pronunciation?
 Mike in Japan's reply was promoted to an answer.
I think our Guest merely meant to ask what "a." stands for when it's an abbreviation of something, to which I must answer that it depends on the context. Where did you find it?
"a" is an articile.
Teachers: We supply a list of EFL job vacancies
Is 'A' an adjective?
Is 'a' or 'an' used as adjective.