A childhood belief about sex

When I was five, I asked my Sunday school teacher to define "fornication". She said it meant to use bad words. I believed her until I was a thirteen when my classmate were talking about a woman who had fornicated and therefore had sinned. I said I didn't think saying bad words should be considered a sin. They looked at me as though I were crazy and explained the concept. I still went to the dictionary to find out for sure.