The type of *expression* should match the declared return type of the function; in the above example, the return type is Number and we see that the return expression `x * x` is a Number since the input parameter `x` is a Number.
### Storing the returned value
The following code calls the `square` function with the number 42 and stores the output parameter in the `result` variable:
```
let result1 = square(42)
```
`result` is the default variable name for the function output, as specified in the function