Best definition
Your Name – usually used in fan fictions so that you are the main character

“Y/N!” lindsay called, “where are you?”

“be right down”

“we’re gonna be late Y/N!”
Y/N: define #2
Sometimes used in fan fictions for abbreviating “your name”

It can also stand for yin, An amazing name.
Person: Hey y/n

Yin: my names yin
Y/N: define #3
“Y/N” usually proceeds an interrogative or question made by one party asked to another party or individual. Simply, it means ‘yes’ or ‘no’. Sometimes, individuals use ‘y/n’ for arbitrary means, such as adding ‘y/n’ to statements that are not interrogatives or questions.
Correct use of Y/N?: Should she get gastro bypass surgery, y/n?

Answer: Y as in yes if the person needs it and it’s good for their health.

N if the person is borderline skinny or can possibly lose the weight without going under the knife, or just in general.

Incorrect use of Y/N?: She is so overweight she can barely move. The doctor said she needs gastro bypass surgery, y/n?

Y/N: define #4
Saying y/n parodies the old DOS programs people used back in the day. It means yes/no, and some geeks still use it when they ask questions.

For example:
“you want me send you that file y/n?”

“you wanna come out y/n?”

“y halo thar buttsecks y/n?”