```r
x  # this is a valid name
descriptive_name   # descriptive names are preferable
                   # - note the underscore separating the words
                   # - spaces are not allowed
also.valid  # This is also a valid name, using an older and maybe
            # confusing naming scheme. If you come from Java/C++/Python/Javascript....
            # the . in the middle of the name is *not* the member access operator
```