Improper mathematical behavior

Special K: Did you know that fractions expressed as a numerator and denominator are called vulgar fractions? I didn't.

b1-66er: I did not. 

What's the opposite?

A "proper" fraction?  And what does it consist of. 

K: A "decimal fraction."

Not sure how widespread those terms are. I learned it from that 0/3 Unicode thing. 

b1: Gimme an example, please.

K: Any decimal. 0.5, 0.77, etc.

b1: I see. 

Thank you. 

So why use the word "vulgar" to describe the other ones?

K: I haven't found an explanation for that. 

b1: Well work on it, bitch. 

K: No.

b1: https://www.mentalfloss.com/article/21106/obscenity-vs-profanity-vs-vulgarity-whats-difference