What is difference between al malik and maalik (guardian of hell)?

Assalamulekum wa rahmatullah wa barkatahu I m from india. I m really confused now a days. That al malik is 99 names but there is also angel names maalik who is also guardian of hell.both of the word look like same to me. So what i should use respectful word when i making dua? What if i made mistake by using similar word? Please explain me so i can understand. Thank you.