[1] "Aiya!" - the quintessential Cantonese expression, so common that it is adopted by other cultures. It can signify surprise, pain, disappointment, frustration, anger, indignation and more, depending on inflection and context. You are just as likely to hear this word uttered by youngsters playing computer games as you are by a grandmother scolding children. Note: [ai1 jaa1] is the more common pronunciation; [ai1 jaa3], [ai1 jaa5] & [ai6 jaa4] are less common.
[2] It is used before a kinship term, e.g. father, uncle, etc.