The function takes a string input and returns the length of the string as a written out word.

[CODE]:
```python
def approx_function(s):
    word_lengths = ["zero", "one", "two", "three", "four", "five", "six", "seven", "eight", "nine", "ten",
                    "eleven", "twelve", "thirteen", "fourteen", "fifteen", "sixteen", "seventeen", "eighteen", "nineteen"]
    return word_lengths[len(s)]
```

Please let me know if you want to test any more inputs with the original function.