Does the output in a relation have to be differet for it to be a function?

A function is one-to-one which means every x-value or member of the domain can only have exactly one output. but, there is no law that says they cannot share an output.

think of it like bridges from inputs to outputs. for it to be a function, there has to be one bridge leaving each input. we dont care where it goes, just that it goes.