the letters ). Some linguists use the terms diphthong and triphthong only in this phonemic sense. Written vowels The name "vowel" is often used for the symbols that represent vowel sounds in a language's writing system, particularly if the language uses an alphabet. In writing systems based on the Latin alphabet, the letters A, E, I, O, U, Y, W and sometimes others can all be used to represent vowels. However, not all of these letters represent the vowels in all languages that use this writing, or even consistently within one language. Some of them, especially W and Y, are also used to represent approximant consonants. Moreover, a vowel might be represented by a letter usually reserved for consonants, or a combination of letters, particularly where one letter represents several sounds at once, or vice versa; examples from English include igh in "thigh" and x in "x-ray". In addition, extensions of the Latin alphabet have such independent vowel letters as Ä, Ö, Ü, Å, Æ, and Ø. The phonetic values vary considerably by language, and some languages use I and Y for the consonant , e.g., initial I in Italian or Romanian and initial Y in English. In the original Latin alphabet, there was no written distinction between V and U, and the letter represented the approximant and the vowels and . In Modern Welsh, the letter W represents these same sounds. Similarly, in Creek, the letter V stands for . There is not necessarily a direct one-to-one correspondence between the vowel sounds of a language and the vowel letters. Many languages that use a form of the Latin alphabet have more vowel sounds than can be represented by the standard set of five vowel letters. In English spelling, the five letters A E I O and U can represent a variety of vowel sounds, while the letter Y frequently represents vowels (as in e.g., "gym", "happy", or the diphthongs in "cry", "thyme"); W is used in representing some diphthongs (as in "cow") and to represent a monophthong in the borrowed words "" and "" (sometimes cruth). Other languages cope with the limitation in the number of Latin vowel letters in similar ways. Many languages make extensive use of combinations of letters to represent various sounds. Other languages use vowel letters with modifications, such as ä in Swedish, or add diacritical marks, like umlauts, to vowels to represent the variety