What term describes two vowels that produce two sounds gliding into one another?

The term that describes two vowels that produce two sounds gliding into one another is a diphthong. Diphthongs involve the blending of two vowel sounds within the same syllable, creating a single, gliding sound. For example, in the word "coin," the vowel sounds 'o' and 'i' combine to create a sound that is distinct from each individual vowel. This characteristic of diphthongs is essential for understanding how they function in language and how they differ from other vowel combinations.

Vowel digraphs, in contrast, consist of two vowels that together typically create a single sound, such as 'ee' in "see." A diphthong vowel cluster is not a standard term used in linguistic terminology, while vowel combinations may refer more broadly to any two vowel sounds together, but do not specify the unique characteristic of the sound gliding. Hence, recognizing diphthongs is crucial for phonics and literacy instruction, especially for early learners who are developing their understanding of vowel sounds and relationships.