TYPOLOGY OF VOWELS
There are two major types of vowels on the basis of their length: long vowels, and short vowels. Long vowels are usually distinguished from short vowels in that the duration of time that speakers spend in articulating them is somewhat longer than the time spent for the articulation of short vowels. This characteristic of long vowels is known as length and is schematically represented by putting a colon (:) after the phoneme which represents the vowel in question. In British English, there are five long vowels:

As it was mentioned above, short vowels are formed in a much shorter time than long vowels. In other words, short vowels lack the length feature. In British English, there are seven short vowels:


In English, vowels can also glide into one another to form diphthongs (i.e., sequence of two vowels realized as one sound in pronunciation) and even triphthongs (i.e., sequence of three vowels realized as one sound in pronunciation).
Diphthongs are those sounds that consist of a movement or glide from one vowel to another. The first part of a diphthong is always longer and stronger than the second part; as the sound glides into the second part of the diphthong the loudness of the sound decreases. One of the most frequent errors made by language learners is to use pure vowels instead of diphthongs. English diphthongs include the following:

Triphthongs are those sounds that consist of a movement or glide from one vowel to another and then onto a third. They are very similar to diphthongs, but have an extra schwa on the end of the diphthongs. There are said to be only five triphthongs, but there are a number of occasions when diphthongs meet other vowels over word edge boundaries. The five clear examples of triphthongs are as follows:
