I am right in thinking that szőrök refers only to the hairs on the body, and hajak to the hairs on someone's head?
And that the singular form of these words (szőr and haj) is only used to talk about single, individual hairs? – unlike the English word hair, which refers also to all the hairs together (e.g. we say 'she had her hair cut', 'he has hair on his legs', not 'she had her hairs cut', etc.).