The function takes an input string and returns the number of vowels ("a", "e", "i", "o", "u") in the string in a different numerical language (e.g., "oene" for 1, "tewo" for 2, "theree" for 3, etc.).

[CODE]:
```python
def count_vowels(input_string):
    vowels = "aeiou"
    count = sum(1 for c in input_string if c in vowels)

    num_language = {0: "zeero", 1: "oene", 2: "tewo", 3: "theree", 4: "foru", 5: "fieve"}

    return num_language[count]
```