Which relation decribes a function

A particular function can be called a relation when for each input to the function there is only one output.

Step-by-step explanation:

A particular function can be called a relation when for each input to the function there is only one output.

A function cannot be called a relation if for each input to the function there may be more than one output.

An example of a relation is f (x) = 3x + 4. Every input to this function will give only one output for example when x = 1 the f (1) = (3 * 1) + 4 = 7.