Vowel whose quality does not change over the duration of the vowel is called a monophthong. Monophthongs are sometimes called "pure" or "stable" vowels. A vowel sound that glides from one quality to another is called a diphthong, and a vowel sound that glides successively through three qualities is a triphthong. All languages have monophthongs and many languages have diphthongs, but triphthongs or vowel sounds with even more target qualities are relatively rare cross-linguistically. English has all three types: the vowel sound in "hit" is a monophthong , the vowel sound in "boy" is in most dialects a diphthong , and
Caudron Types M and N Caudron Types M and N The Caudron Types M and N were small, fast French sports monoplanes, flown 1911–13 under a wide range of engine powers. There was also a military version. Although almost all the aircraft designed by the Caudron brothers in the twenty years from their first attempts in 1908 were biplanes, they did in 1911-2 produce three monoplane types. These were the single seat racing Types M and N and the related but somewhat larger Type M2 military version. The Types M and N were very similar and, though the designations were reported together with some details