Ukrainian questions

Прiвит Kolbaskina and all.

I have a simple question about ukrainian language. In my book, a mysterious declination appears and until now there's not explanation. Look the dialogue from the book

Тарас: Добрий вечiр. Як життя?
Стiвен: Нормально, дякую. Вiро, познайомся: це мiй друг Стiвен.
Вiра: Дуже приемно, Вiра.
...
Тарас: О! ... Лiдо, яка зустрiч! Вибач, будь ласка!
Лiда: Добрий вечiр, Тарасе!

So Вiра changes to Вiро and Лiда changes to Лiдо . Is it a special case?. If yes, could you explain also when should I use it and what are the rules?

Дуже дякую!

She hasn't been around for a while so I'll try:

That is the vocative case (I think) that has been discussed in the Russian off-topic thread

http://www.allthelyrics.com/forum/ru...sations-3.html

posts 68-76

Oh thank you very much. Probably the book will teach something about but I was very lazy to run through its 400 pages and look for it.