As a substitute for "Bro", many would say "Girl". Using a person's name always works.
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In normal conversation with male, we often use the word "Bro, how are you?" Suppose it is a female I am talking to, what are the substitute word for "bro"? I know the word "Sis" but it sounds odd. Or should I just say her name? or "M'am"? please advice.
I have never referred to anyone as "Bro", nor am I ever likely to.
"Invading armies have no rights." Noam Chomsky
There's no simple answer, NewEnglish1. It depends how old you are, how old the female is, what your relationship is with her, and how polite/respectful/flirtatious you want to be.
"Ma'am" has always worked well for me.
It's polite, safe, respectful, works for any age or station, and usually comes across as charming if nothing else.
If the woman in question is still a young girl, then I will use 'Miss".
Only once have I heard a woman object to being called "Ma'am". A friend in college came by studio looking for me. When he didn't immediately see me, he approached a woman working in the studio with "Excuse me, Ma'am" to inquire if I was around.
She took offense because she felt it made her feel old. Not sure what else my friend was supposed to say.
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We don't use "Ma'am" in BrE in this context. Some people say "Madam" if they don't know the name of the person they're addressing but, like the person in the post above, a younger person might take offence at that because it does sound like something you say to an older woman.
I don't use anything if I don't know someone's name. I simply say "Excuse me". In the situation above, I would have approached the woman in the studio and simply said "Excuse me. Is Skrej around?"
Remember - if you don't use correct capitalisation, punctuation and spacing, anything you write will be incorrect.
People in a service role (wait staff, receptionists, front-desk clerks, etc) may use them, as may police and customs officers (although with these last two the 'respectful' form of respect often implies no respect at all), but strangers do not generally use any form of address.
I agree with Piscean that not using any form of address is fine in most contexts in British English, but I do still use sir and madam sometimes, though I don't use miss.