uvr wrote:That's not entirely true. "apan" is also used to mean 'our' (i.e., apna अपना) in some dialects of Hindi -- so it may depend on the context how it is used.
But, in the general sense, you are right -- apun/apan are part of Mumbai slang, not of mainstream Hindi/Urdu.
UVR, firstly good to see you here, glad you joined after I told you about this site and how passionate about learning the members here seemed to be.
Hassaan sahab and Meera-ji:
Being from Bombay/Mumbai a long while ago myself, I thought I would share a little more on this word "apun".
UVR is right in that in that "apan" (note: NOT "apun") can be used for "we" in other dialects. However, if you heard this word in some bollywood movie, you likely heard it as "apun" for "maiN" or "apun ko" for "mujhe/mujh ko." This is certainly slang, and I recommend to all students of the language to strictly AVOID using it in all cases. Growing up in Mumbai and speaking the regional colloquial, I too used the word -- but it would seen as "crass" by others.
Interestingly, I recently had a conversation with people in Mumbai about the slang in use now, and I have been told (I have not been back in a while now) that "my knowledge of Mumbai slang" is now outdated, and people are talking "differently," even on the streets (compared to the 70s and 80s) - the word "apun" is slowly vanishing from the vocabulary of the common man there, and the Mumbai slang now seems to contain more influences from "Goan" (west coast province Goa) and "Punjabi". Punjabi (or what is perceived by Bollywood for it) seems to be the "fashion" now.
Don't know if this tidbit is useful at all (it was to me). In general, more formal/proper language would be the way to go in all cases. Can hardly go wrong there.
Hope that helps.