We grow up being told at a, e, i, o and u are vowels. But that is not the whole story. These letters are used in multiple ways to make multiple vowels sounds. English has many vowels sounds such as the sound “ow” in cow, “ew” in new, “ei” in weight and so on. The IPA (the International Phonetic Association) has many characters for vowels and those can be put together to create even more vowel sounds (called dipthongs). So there are way more than just 5 vowels.