거울 is just a mirror, you add 'a' when you call it 거울아 is how we call it. For example 소현(Sohyun) is just a name itself, but when you want to call her name it has to be 소현아(Sohyun-a).
if any words end with a vowel, then you put 'ya'. For example 현아야(Hyuna-ya), 바보야(Babo-ya)(babo:fool)

YOU ARE READING
Learn Korean
RandomAs the title says, here you can learn Korean ;) Note: I'm not Korean I'm trying to learn it too and I try to be as careful as possible by using data from various websites not only from one. If you think something is wrong or there are more ways to...