Hello & Welcome
Ahlan !  

The following 2 greetings are the most common greetings in Egypt when meeting people you know or you do not know, in formal or non-formal situations alike;

1- Ahlan wa Sahlan which means “hello” and “welcome”

This is the most common greeting which can be used to greet someone you just met or someone you know really well. It is very general greeting but you can hear it often in daily conversations, in welcoming guests or visitors as well as in responding to someone who just introduced themselves.   

The Response is always ahlan bīk/beek (talking to a male) or bīki/bīki (talking to a female) or bīku/bīku (plural/group of people).

The reason for the variations is the fact that there are 3 different versions for the word ‘You’ in Egyptian Arabic based on gender and number of the addressed person;

Inta à talking to a male

Inti à talking to a female

Intu à talking to a group of people

You can say it also when welcoming someone to your home, country or place of work. 

Alternatively you can always say just "Ahlan" to mean simply "hello."

This is how it is written in Arabic alphabet;     أهلا وسهلا

2- MarHab or MarHaban which can be used the same way to give the same meaning as ahlan wa sahlan.

 The Response is always Marhab (or Marhaban) bīk/beek (talking to a male) or bīki/bīki (talking to a female) or bīku/bīku (plural/group of people).

Same like Ahlan wa Sahlan can be used also when welcoming someone to your home, country or place of work.

Here is how you write it in Arabic;  مرحبا or مرحب

3- As-salāmu 3aleikum

The most common and popular greeting in Arabic used all over the Arabic-speaking countries is As-salāmu 3aleikum which literally means Peace be upon you,  it can be used as a general greeting all day long regardless of the time. It is used by majority of Muslims and some Christians use it as well… it used to be said by Muslims only as a religious greeting but nowadays it became neutral used by non-Muslims as well.

Here is how you write it in Arabic;  عليكم السلام

The Response: w3aleikum as-salām and some devout Muslims like to add waraHmatu llāhi wabarakātu - which means and God's mercy and blessings.

The good thing about this greeting is that it is NOT gender or number specific meaning that both the greeting and the response can be used with men, women or groups all the same way…