This is a de facto Irish-English word, an affirmative exclamation. It consists of a rapid insuck of air, and sounds a bit like a gasp. Sometimes it is pronounced a bit like "yeah;" but not always. Most common amongst women.
Irish men will often greet with a sideways nod when passing on the street. This is usually accompanied by an audible gesture, whether a click of the tongue or a verbal greeting.
Use of one's given name
If an Irish person knows your first name, he or she will probably call you that, even without introduction.
Small-talk in Ireland is an important part of most normal interactions....
Eyes to heaven
An uptoss of the chin accompanied by a slight click from the tip of the tongue and a "you know y'rself" rolling of the eyes upward.... This expresses acknowledgement of the sublime and ridiculous nature of reality.
The Irish have difficulty making a formal complaint....
"Yeah but sure "what can you do?..."