Diphtongeja

Diphtongeja, or diphthongs, are vowel sounds that begin with one vowel and glide to another within a single syllable. They differ from sequences of two separate vowels (hiatus) and from simple monophthongs, which have a single, steady articulation. In many languages, diphthongs are phonemic, meaning they contrast with pure vowels and can change word meaning.

Articulation and structure commonly involve two elements: a nucleus (the starting vowel) and an offglide (the ending vowel or semivowel). The glide is produced without a full break, giving a characteristic sonic movement. Diphthongs can be described by the relative height and frontness of the starting and ending vowels, as well as whether the ending is higher, lower, or more central than the start. Some analyses distinguish rising diphthongs (ending higher than they start) from falling diphthongs (ending lower). Centring diphthongs, which move toward a mid central vowel, are a subtype found in several languages.

Examples from English illustrate typical diphthongs: the word bite has a rising vowel sound [aɪ], rain [eɪ], and boy [ɔɪ]. House often contains [aʊ], and go [oʊ] or [oʊ̯] depending on the dialect. Languages vary widely in which diphthongs occur and how they are realized; some languages have many phonemic diphthongs, while others treat such sounds as sequences of a vowel and a semivowel rather than single phonemes.

Historical and cross-linguistic perspectives show that diphthongs can arise from vowel shifts or glide insertions and may later monophthongize in some dialects. They remain a key feature in the vowel inventories of many languages.