Qurstion - Names of Allah.

Okay so I have a book that has 99 names of Allah. And it has names like Ya Sami, Ya Lateef, Ya Mujeeb. But there are a few words which say Ya-(and then the name) in english but underneath at times its AL-(and the name). I have also read here and on various sites that its said to recite Ya-lateef as Ya lateefo, Ya Mujeeb as Ya Mujeebo and so forth…yeh confusion please door karo meri. Chakkar kiya hai? Does pronouncing the names differently change the meaning/effects of the Name/word? Does right and wrong count in this case?