Diphthong
A diphthong (/ˈdɪfθɒŋ, ˈdɪp-/ DIF-thong, DIP-;[1] from Ancient Greek δίφθογγος (díphthongos) 'two sounds', from δίς (dís) 'twice', and φθόγγος (phthóngos) 'sound'), also known as a gliding vowel, is a combination of two adjacent vowel sounds within the same syllable.[2] Technically, a diphthong is a vowel with two different targets: that is, the tongue (and/or other parts of the speech apparatus) moves during the pronunciation of the vowel. In most varieties of English, the phrase "no highway cowboy" (/noʊ ˈhaɪweɪ ˈkaʊbɔɪ/) has five distinct diphthongs, one in every syllable.
Diphthongs contrast with monophthongs, where the tongue or other speech organs do not move and the syllable contains only a single vowel sound. For instance, in English, the word ah is spoken as a monophthong (/ɑː/), while the word ow is spoken as a diphthong in most varieties (/aʊ/). Where two adjacent vowel sounds occur in different syllables (e.g. in the English word re-elect) the result is described as hiatus, not as a diphthong.
Diphthongs often form when separate vowels are run together in rapid speech during a conversation. However, there are also unitary diphthongs, as in the English examples above, which are heard by listeners as single-vowel sounds (phonemes).[3]
Types[edit]
Falling and rising[edit]
Falling (or descending) diphthongs start with a vowel quality of higher prominence (higher pitch or volume) and end in a semivowel with less prominence, like [aɪ̯] in eye, while rising (or ascending) diphthongs begin with a less prominent semivowel and end with a more prominent full vowel, similar to the [ja] in yard. (Sometimes, however, the terms "falling" and "rising" are used, instead, to refer to vowel height, i.e. as synonyms of the terms "closing" and "opening".[9] See below.) The less prominent component in the diphthong may also be transcribed as an approximant, thus [aj] in eye and [ja] in yard. However, when the diphthong is analysed as a single phoneme, both elements are often transcribed with vowel symbols (/aɪ̯/, /ɪ̯a/). Semivowels and approximants are not equivalent in all treatments, and in the English and Italian languages, among others, many phoneticians do not consider rising combinations to be diphthongs, but rather sequences of approximant and vowel. There are many languages (such as Romanian) that contrast one or more rising diphthongs with similar sequences of a glide and a vowel in their phonetic inventory[10] (see semivowel for examples).
Sound changes[edit]
Certain sound changes relate to diphthongs and monophthongs. Vowel breaking or diphthongization is a vowel shift in which a monophthong becomes a diphthong. Monophthongization or smoothing is a vowel shift in which a diphthong becomes a monophthong.
Difference from semivowels and vowel sequences[edit]
While there are a number of similarities, diphthongs are not the same phonologically as a combination of a vowel and an approximant or glide. Most importantly, diphthongs are fully contained in the syllable nucleus[13][14] while a semivowel or glide is restricted to the syllable boundaries (either the onset or the coda). This often manifests itself phonetically by a greater degree of constriction,[15] but the phonetic distinction is not always clear.[16] The English word yes, for example, consists of a palatal glide followed by a monophthong rather than a rising diphthong. In addition, the segmental elements must be different in diphthongs [ii̯] and so when it occurs in a language, it does not contrast with [iː]. However, it is possible for languages to contrast [ij] and [iː].[17]
Diphthongs are also distinct from sequences of simple vowels. The Bunaq language of Timor, for example, distinguishes /sa͡i/ [saj] 'exit' from /sai/ [saʲi] 'be amused', /te͡i/ [tej] 'dance' from /tei/ [teʲi] 'stare at', and /po͡i/ [poj] 'choice' from /loi/ [loʷi] 'good'.[18]