Diphthongization is a phonetic process where a single vowel sound changes into a complex vowel sound, known as a diphthong. This occurs when two vowel sounds are pronounced in a single syllable, creating a glide from one sound to another. For example, the vowel sound in the word time shifts from a pure vowel to a combination of sounds, resulting in a diphthong. This phenomenon is common in many languages and can affect pronunciation and meaning. In English, diphthongization can be observed in words like coin and loud, where the vowel sounds blend together. Understanding diphthongization helps in grasping the nuances of speech and language development.