"I am a boy."
Překlad:Já jsem chlapec.
Not really. There is also a word 'hoch' that means the same. Kluk is probably slightly more colloquial. Though not improper. Chlapec sounds very proper but than I am from Prague and use 'kluk' more but people from Moravia are likely to use 'chlapec' more. 'hoch' sounds pretty archaic.