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
Types of membership of Opus Dei etc. Typically, the supernumeraries of the Opus Dei prelature are married men and women who have secular careers and lead traditional family lives. Supernumeraries devote a portion of their day to prayer, in addition to attending regular meetings and taking part in activities such as retreats. Due to their career and family obligations, supernumeraries are not as available to the organization as the other types of members, but they typically contribute financially to Opus Dei, and they lend other types of assistance as their circumstances permit. Unlike other types of members, supernumeraries are not required to be celibate. Numeraries, the