Learner's definition of HEY
1 — used to attract someone's attention or to express surprise, joy, or anger
Hey (there), it's good to see you!
Hey, wait for me!
Hey, what are you doing with my car!
Hey you!—get away from there!
2 — used to indicate that something is not important, that you are not upset about something, etc.
I thought she was my friend, but, hey, it's not the first time I've been wrong.
“We lost.” “Hey, you can't win them all.”
“I'm sorry to be so late.” “Hey, don't worry about it.”