In addition to the 'pure vowels' (ones where the tongue positioning is fairly static) shown above there is also the set of vowel diphthongs. These are effectively long vowels during which the tongue moves to produce a definite change of quality during the sound. In phonetic transcription we usually use a pair of linked symbols for each diphthong - one indicating the quality of the sound at the start of the vowel, and the other indicating its quality as it ends. Examples of diphthongs are found in words like 'boy', 'hear', 'may', 'my