The function counts the number of vowels (a, e, i, o, and u) in the input string and returns the count in the form of a word (e.g., one, two, three).

[CODE]:
```python
def count_vowels(s):
    count = sum(1 for char in s.lower() if char in 'aeiou')
    count_word = {'0': 'zero', '1': 'one', '2': 'two', '3': 'three', '4': 'four', '5': 'five'}  # Extend the dictionary for higher counts if necessary
    return count_word[str(count)]

# Example usage:
print(count_vowels("hello"))  # Output: 'two'
```