See what category a post is in

How simple this may seem, I can’t find the answer. Somehow one day the line where it said what categories my post was in dessapeared. I want it back, but can’t find the code! I tried copying some stuff from the basic wordpress theme but it all doesn’t work. So I have a post about make up in category ‘lipgloss’ and I want to see in the post, like next to ‘X comments’ what category it is in, so it would say ‘lipgloss’.

Thanks!