This document discusses diphthongs in Dutch, listing common diphthongs and their pronunciations in Netherlandic and Belgian Dutch. It also provides a definition of a triphthong as a monosyllabic vowel combination that involves a smooth articulatory movement between three vowel qualities in quick succession, with each diphthong or triphthong having a specific number of target articulator positions.

5. Diphthongs of Dutch
Netherlandic[9] Belgian[10]
zeis [ɛɪ̯]
ui [œʏ̯]
zout [ʌʊ̯] [ɔʊ̯]
beet [eɪ̯] [eː]
neus [øʏ̯] [øː]
boot [oʊ̯] [oː]

6. "triphthongos", literally "with three sounds," or "with three
tones") is a monosyllabic vowel combination involving a quick but
smooth movement of the articulator from one vowel quality to
another that passes over a third. While "pure" vowels,
or monophthongs, are said to have one target articulator
position, diphthongs have two, and triphthongs three.