Here are some possibilities:
1. Considering only the order of vowels:
* Using all 5 vowels (A, E, I, O, U): There are 5! (5 factorial) = 120 ways to arrange them.
* Using any number of vowels: This gets more complex. You'd need to consider combinations of 2 vowels, 3 vowels, etc., and the total number of combinations would be quite large.
2. Considering sounds instead of letters:
* In English, there are around 20 vowel sounds. The number of combinations you could make depends on how many vowels you allow in a combination and if you allow repeats. For example, "ee" and "oo" are common vowel combinations.
3. Considering syllable structure:
* Vowel combinations are often part of syllables. The structure of a syllable can influence which vowel combinations are possible. For example, some languages allow vowel combinations in the middle of syllables, while others only allow them at the end.
Therefore, there is no single answer to your question. To give you a more specific answer, I need to know:
* How many vowels are allowed in a combination?
* Do you want to include all possible vowel sounds, or just those represented by letters?
* What rules are we following about the order of the vowels and syllable structure?