2. Monovowel is a vowel composed of one vowel, also called monophthong. The parts of Chinese pronunciation except initials and tones are called vowels, which can be divided into monosyllabic vowels, complex vowels and nasal vowels according to their structures. There are thirty-nine vowels in Putonghua, and the pronunciation characteristics of single vowels are consistent in mouth shape and tongue position from beginning to end.