One of the tensest moments I ever had working in retail was serving a customer during the lunch-time rush. It was particularly busy, as that day this residential street in Central London was throwing a street party for the Queen's Jubilee. I could see quite clearly that this fan of Twixes was a woman - there was no doubt about it - but what slipped out of my mouth as she peered into her purse for change was a cheery "good morning, sir!". I was as shocked as she was, and the proverbial cat had such grip on my tongue that I couldn't even apologise.
Of course, it's rare to confuse someone's gender. But, as I have been discovering, Egyptian Arabic is has far more cultural landmines when it comes to addressing people than English does. The title you use depends not just on gender, but on other characteristics that in English would be considered a breach of political correctness, such as age, religion and social class.
My first lesson in this came in thanking my taxi driver with the form of address that I've been using daily at university for the past two years: يا استاذ | yā ustāz, which literally translates as professor (c.f. Spanish "usted", the polite second person pronoun). Of course the man wasn't a professor, but as I understood it, it is a polite term that could be used in other situations too. "انا مش استاذ | ana miš ustāz | I'm not a professor," he replied, in such a way that he clearly thought I was being sarcastic.
I learnt later that although the term extends beyond actually professors, it is still only used for middle class people with a formal education. Despite my belief that the knowledge of a taxi driver is probably quite extensive, especially in the realms of local geography and history, social mobility seems so non-existent in Egypt that the term couldn't even come across as a polite gesture of solidarity. People know their places and I must learn to recognise them too.
The second term that got me into trouble is يا حاجة | ya hagga, which literally means pilgrim but is used to address elderly Muslim women who have probably lived long enough to have undertaken the pilgrimage to Mecca. The woman I was sharing a lift with wore a niqab, so I didn't have much to go by, other than that she was clearly a Muslim woman. When I asked which floor she needed, addressing her with this term, she let out a giggle that suggested she was probably no older than me.
Not wanting to reproduce what's already well documented elsewhere on the internet, I will provide this link for a more complete list of the many, and sometimes surprising, forms of address in Egyptian Arabic.
One term that they don't include is يا برنس | ya brins, a corruption of the English word prince, a playful but polite way of addressing young men. Recently, trying to tell an teenager that I didn't want to buy the friendship bracelet he was offering me, I accidentally addressed him as كابتن | kaptin | captain, which is used for younger children, which clearly got on his pubescent nerves. Sometimes offending people is the best way to ensure you won't forget a word again.