Is it a function or not a function?

Answer:
Not a function
Step-by-step explanation:
Fails the vertical line test
Answer:
No a circle is not a function.
Step-by-step explanation:
A function is a mapping from 1 set to another
eg, 1 to 2
3 to 4
while a circle it maps the same point to another
meaning it has more than two input/output
(if u get what i mean)