It's not a proper conversation with an Arab if the word ya3ni doesn't come up ... at least once. 

But, there are hundreds of people who aren't too familiar with the word, specifically its very different meanings and uses.

Here's a basic guide: 

Level 1: Placing emphasis

When is it used?

When you want to place emphasis on a previous word, BGADD ya3ni

Level 2: Giving an explanation

When is it used? 

When you want to explain something ... ya3ni ... without adding unnecessary words .

"Fa ya3ni" ... this is what it means.  

Level 3: Asking for a favor

When is it used?

When you want the world to collectively do you a favor kind, please ya3ni

The kind of ya3ni that resorts to begging, without the destruction to your dignity.  

Level 4: Defining words

When is it used?

When you want to try and explain a certain idea, word or tradition to someone, this is the ya3ni you use.

This is the true definition of the word ya3ni, ya3ni. 

Level 5: Expressing anger

When it is used? 

When you're too angry to even talk, ya3ni. 

Two words: KEEF YA3NI!!!!! 

Level 6: Expressing more anger

When is it used? 

When you're too angry to even talk ... so you just say stop already ya3ni.

Level 7: Expressing extreme anger

When is it used? 

When you're so upset words fail you ... so ya3ni becomes your go-to expression when you just want to cut things short