Vowel is a sort of sound which no closing of the throat or mouth occurs anytime vocalization. The vowels can be contrasted with the consonants, the sounds which one or more points where the air is stopped. In almost all languages, the words contain at least one vowel. If one word can be formed without consonants - such as English or the words I mean - no password may consist of consonants without a vowel.
Vowels in many languages are not essential in the general sense. On the contrary, a vowel in the following languages - many of which are Semitic languages - acts more to give a bow to the word to distinguish that other individual words. A parallel to this in English can be seen in the example of diving and dove and lay and lie, where the base word is the same but the vowel change means tense. Languages that this type of structure are often not even make all their vowels in written text. Arabic and Hebrew are good examples of this, when marking a lot of vowels is not required in writing.
Since a vowel refers to a type of sound, the spelling of the letters stand for a consonant in certain circumstances, a vowel in others. In English, we see the letters Y and W are most often used for consonants, but can also be used to represent vowels. In the case of y, for example, can you compare its use in there, words per day. In the word there, it acts as a single consonant with the center of the tongue blocks the air flow on one side touching the palette of the mouth - this is called a palatal approximant. In the word day, on the other hand, is formed as a vowel when the word was written in English as dei.
In the case of w, we can examine the words and how to woo. In the word woo the letter serves as a consonant, with the back of the tongue blocks the air flow on one side touching the palette of the mouth - called approximate labiovelar. In case the word as a vowel, which can be represented by like hao written English.
In English, there are five letters still a vowel when it is written: a, e, i, o, u. These five letters and accounts for more than five vowels, however, as the word, or in combination with other vowels. Compare the letter in the words hat and hate as one of many examples.