Answer
function
Work Step by Step
The relation is a function because to each input value there belongs at most $1$ output value. (The output values belonging to different inputs don't have to be unique.)
You can help us out by revising, improving and updating this answer.
Update this answerAfter you claim an answer you’ll have 24 hours to send in a draft. An editor will review the submission and either publish your submission or provide feedback.