small cat= kotek young cat = kociak, kocię, kociątko
I do not know many cats but I think while kocię and kociak are literal translation for kitten, kotek is often used. Kociątko- is a diminutive from kocię.
Also kociak is a word for pretty girl/young woman. ( like chick )
and kotek is an often used endearment used for both genders. (like honey)