What is the sound called when one vowel blends into another within a single syllable?

• A. diphthong
• B. monophthong
• C. digraph
• D. trigraph

Answer: (A)

The sound is a diphthong. A diphthong is a vowel sound that starts with one vocal quality and glides into another within the same syllable, so your mouth moves from the position of the first vowel to the second as you say it. Examples in English include the /aɪ/ sound in time, the /ɔɪ/ sound in coin, the /eɪ/ sound in bay, and the /aʊ/ sound in house. This glide distinguishes it from a monophthong, which stays on a single vowel sound, and from digraphs or trigraphs, which are about two or three letters representing sounds rather than the vowel’s changing quality within a syllable.