triphthong

This term is primarily used in linguistics and phonetics to describe a complex vowel sound. It is a more rare occurrence than a diphthong, which consists of only two vowel sounds. The term is technical and typically appears in academic discussions of phonology or dialectology rather than in casual conversation.

Because it describes a specific phonetic unit, it is treated as a standard countable noun. When discussing multiple instances of these sounds across different words or languages, the standard plural form is used.