“Fire,” “dire,” and “Ireland” showcase the triphthong well, as the “ire” sound constitutes the triple vowel intonation.

Triphthongs allow a vowel to travel through three sounds within a single syllable. The word “oil” showcases this well: the “o” changes sounds as it slides into the “i” beside it. Then there are the diphthong, wherein a vowel sound glides from one to the next (they’re also referred to as gliding vowels) in a single syllable. The “o” in hop is an example of this, as is the “i” in hit. Vowels articulated the same way from beginning to end in a single syllable are called monophthongs. Vowels can change sounds over the course of their pronunciation, just as they can also remain entirely the same. And it’s in this second definition, called the phonological definition, where what we think of as standard vowels (a, e, i, o, and u) become more complicated with the “sometimes y” and, yes, “sometimes w.” The phonetic definition and the phonological definition of a vowel are not always the same.

What makes a vowel a vowel