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A diphthong ( /ˈdɪfθɒŋ/ or /ˈdɪpθɒŋ/;^[1] Greek: δίφθογγος, diphthongos, literally "two sounds" or "two tones"), also known as a gliding vowel, refers to two adjacent vowel sounds occurring within the same syllable. Technically, a diphthong is a vowel with two different targets: That is, the tongue moves during the pronunciation of the vowel. In most dialects of English, the words eye, hay, boy, low, and cow contain diphthongs.

Diphthongs contrast with monophthongs, where the tongue doesn't move and only one vowel sound is heard in a syllable. Where two adjacent vowel sounds occur in different syllables—for example, 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).^[2]

International Phonetic Alphabet[link]

In the International Phonetic Alphabet, monophthongs are transcribed with one symbol, as in English sun [sʌn]. Diphthongs are transcribed with two letters, as in English sign [saɪ̯n] or sane [seɪ̯n]. The two vowel symbols are chosen to represent the beginning and ending positions of the tongue, though this can be only approximate.

The non-syllabic diacritic (an inverted breve below, ⟨◌ ̯⟩) can be placed under the less prominent component to show that it is part of a diphthong rather than a separate vowel. It is, however, usually omitted in languages such as English, where there is not likely to be any confusion.

Without the diacritic, the sequence [ai] can represent either a diphthong ([ai̯]) or two vowels in hiatus ([a.i]).

Types[link]

Falling and rising[link]

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. (Note that "falling" and "rising" in this context do not refer to vowel height; the terms "opening" and "closing" are used instead. 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 letters (/aɪ̯/, /ɪ̯a/). Note also that 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^[3] (see semivowel for examples).

Closing, opening, and centering[link]

In closing diphthongs, the second element is more close than the first (e.g. [ai]); in opening diphthongs, the second element is more open (e.g. [ia]). Closing diphthongs tend to be falling ([ai̯]), and opening diphthongs are generally rising ([i̯a]), as open vowels are more sonorous and therefore tend to be more prominent. However, exceptions to this rule are not rare in the world's languages. In Finnish, for instance, the opening diphthongs /ie̯/ and /uo̯/ are true falling diphthongs, since they begin louder and with higher pitch and fall in prominence during the diphthong.

A third, rare type of diphthong that is neither opening nor closing is height-harmonic diphthongs, with both elements at the same vowel height.^{[citation needed]} These were particularly characteristic of Old English, which had diphthongs such as /æɑ̯/, /eo̯/.

A centering diphthong is one that begins with a more peripheral vowel and ends with a more central one, such as [ɪə̯], [ɛə̯], and [ʊə̯] in Received Pronunciation or [iə̯] and [uə̯] in Irish. Many centering diphthongs are also opening diphthongs ([iə̯], [uə̯]).

diphthongs may contrast in how far they open or close. For example, Samoan contrasts low-to-mid with low-to-high diphthongs:

• ’ai [ʔai̯] 'probably'
• ’ae [ʔae̯] 'but'
• ’auro [ʔau̯ɾo] 'gold'
• ao [ao̯] 'a cloud'

Length[link]

Languages differ in the length of diphthongs, measured in terms of morae. In languages with phonemically short and long vowels, diphthongs typically behave like long vowels, and are pronounced with a similar length.^{[citation needed]} In languages with only one phonemic length for pure vowels, however, diphthongs may be behave like pure vowels.^{[citation needed]} For example, in Icelandic, both monophthongs and diphthongs are pronounced long before single consonants and short before most consonant clusters.

Some languages contrast short and long diphthongs. In some languages, such as Old English, these behave like short and long vowels, occupying one and two morae, respectively. In other languages, however, such as Ancient Greek, they occupy two and three morae, respectively, with the first element rather than the diphthong as a whole behaving as a short or long vowel.^{[citation needed]} Languages that contrast three quantities in diphthongs are extremely rare, but not unheard of; Northern Sami is known to contrast long, short and "finally stressed" diphthongs, the last of which are distinguished by a long second element.^{[citation needed]}

Difference from a vowel and semivowel[link]

While there are a number of similarities, diphthongs are not the same as a combination of a vowel and an approximant or glide. Most importantly, diphthongs are fully contained in the syllable nucleus^[4][5] 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.^[6] though this phonetic distinction is not always clear.^[7] The English word yes, for example, consists of a palatal glide followed by a monophthong rather than a rising diphthong. In addition, while the segmental elements must be different in diphthongs so that [ii̯], when it occurs in a language, does not contrast with [iː] though it is possible for languages to contrast [ij] and [iː].^[8]

Examples[link]

Germanic languages[link]

English[link]

All English diphthongs are falling, apart from /juː/, which can be analyzed as [i̯uː].

In words coming from Middle English, most cases of the Modern English diphthongs [aɪ̯, oʊ̯, eɪ̯, aʊ̯] originate from the Middle English long monophthongs [iː, ɔː, aː, uː] through the Great Vowel Shift, although some cases of [oʊ̯, eɪ̯] originate from the Middle English diphthongs [ɔu̯, aɪ̯].

Dutch[link]

The dialect of Hamont (in Limburg) has five centring diphthongs and contrasts long and short forms of [ɛɪ̯], [œʏ̯], [ɔʊ̯], and [ɑʊ̯].^[11]

German[link]

Standard German[link]

Phonemic diphthongs in German:

• /aɪ̯/ as in Ei ‘egg’
• /aʊ̯/ as in Maus ‘mouse’
• /ɔʏ̯/ as in neu ‘new’

In the varieties of German that vocalize the /r/ in the syllable coda, other diphthongal combinations may occur. These are only phonetic diphthongs, not phonemic diphthongs, since the vocalic pronunciation [ɐ̯] alternates with consonantal pronunciations of /r/ if a vowel follows, cf. du hörst [duː ˈhøːɐ̯st] ‘you hear’ – ich höre [ʔɪç ˈhøːʀə] ‘I hear’. These phonetic diphthongs may be as follows:

• [eːɐ̯] as in er ‘he’
• [iːɐ̯] as in ihr ‘you (plural)’
• [oːɐ̯] as in Ohr ‘ear’
• [øːɐ̯] as in Öhr ‘eye (hole in a needle)’
• [uːɐ̯] as in Uhr ‘clock’
• [yːɐ̯] as in Tür ‘door’
• [aːɐ̯] as in wahr ‘true’

Bernese German[link]

The diphthongs of some German dialects differ a lot from standard German diphthongs. The Bernese German diphthongs, for instance, correspond rather to the Middle High German diphthongs than to standard German diphthongs:

• /iə̯/ as in lieb ‘dear’
• /uə̯/ as in guet ‘good’
• /yə̯/ as in müed ‘tired’
• /ei̯/ as in Bei ‘leg’
• /ou̯/ as in Boum ‘tree’
• /øi̯/ as in Böim ‘trees’

Apart from these phonemic diphthongs, Bernese German has numerous phonetic diphthongs due to L-vocalization in the syllable coda, for instance the following ones:

• [au̯] as in Stau ‘stable’
• [aːu̯] as in Staau ‘steel’
• [æu̯] as in Wäut ‘world’
• [æːu̯] as in wääut ‘elects’
• [ʊu̯] as in tschúud ‘guilty’

Yiddish[link]

Yiddish has three diphthongs:^[12]

• [ɛɪ̯] as in [plɛɪ̯tə] פּליטה ('refugee' f.)
• [aɛ̯] as in [naɛ̯n] נײַן ('nine')
• [ɔə̯] as in [ɔəf̯n̩] אופֿן ('way')

Diphthongs may reach a higher target position (towards /i/) in situations of coarticulatory phenomena or when words with such vowels are being emphasized.

Norwegian[link]

There are five diphthongs in Norwegian:

• [æɪ̯] as in nei, "no"
• [øʏ̯] as in øy, "island"
• [æʉ̯] as in sau, "sheep"
• [ɑɪ̯] as in hai, "shark"
• [ɔʏ̯] as in joik, "Sami song"

An additional diphthong, [ʉ̫ʏ̯], occurs only in the word hui in the expression i hui og hast "in great haste". The number and form of diphthongs vary between dialects.

Faroese[link]

Diphthongs in Faroese are:

• /ai/ as in bein (can also be short)
• /au/ as in havn
• /ɛa/ as in har, mær
• /ɛi/ as in hey
• /ɛu/ as in nevnd
• /œu/ as in nøvn
• /ʉu/ as in hús
• /ʊi/ as in mín, bý, ið (can also be short)
• /ɔa/ as in ráð
• /ɔi/ as in hoyra (can also be short)
• /ɔu/ as in sól, ovn

Icelandic[link]

Diphthongs in Icelandic are the following:

• /au̯/ as in átta, "eight"
• /ou̯/ as in nóg, "enough"
• /œy̯/ as in auga, "eye"
• /ai̯/ as in hæ, "hi"
• /ei̯/ as in þeir, "they"

Combinations of semivowel /j/ and a vowel are the following:

• /ja/ as in jata, "manger"
• /jau̯/ as in já, "yes"
• /jo/ as in joð, "iodine," "jay," "yod" (only in a handful of words of foreign origin)
• /jou̯/ as in jól, "Christmas"
• /jœ/ as in jötunn, "giant"
• /jai̯/ as in jæja, "oh well"

Romance languages[link]

French[link]

In French, /wa/, /wɛ̃/, and /ɥi/ may be considered true diphthongs (that is, fully contained in the syllable nucleus: [u̯a], [u̯ɛ̃], [y̯i]). Other sequences are considered part of a glide formation process that turns a high vowel into a semivowel (and part of the syllable onset) when followed by another vowel.^[13]

Diphthongs

• /wa/ [u̯a] as in roi "king"
• /wɛ̃/ [u̯ɛ̃] as in groin "muzzle"
• /ɥi/ [y̯i] as in huit "eight"

Semivowels

• /wi/ as in oui "yes"
• /jɛ̃/ as in lien "bond"
• /jɛ/ as in Ariège
• /aj/ as in travail "work"
• /ɛj/ as in Marseille
• /œj/ as in feuille "leaf"
• /uj/ as in grenouille "frog"
• /jø/ as in vieux "old"

Catalan[link]

Catalan possesses a number of phonetic diphthongs, all of which begin (rising diphthongs) or end (falling diphthongs) in [j] or [w].^[14]

In standard Eastern Catalan, rising diphthongs (that is, those starting with [j] or [w]) are only possible in the following contexts:^[15]

• [j] in word initial position, e.g. iogurt.
• Both occur between vowels as in feia and veiem.
• In the sequences [ɡw] or [kw] and vowel, e.g. guant, quota, qüestió, pingüí (these exceptional cases even lead some scholars^[16] to hypothesize the existence of rare labiovelar phonemes /ɡʷ/ and /kʷ/).^[17]

There are also certain instances of compensatory diphthongization in the Majorcan dialect so that /ˈtroncs/ ('logs') (in addition to deleting the palatal plosive) develops a compensating palatal glide and surfaces as [ˈtrojns] (and contrasts with the unpluralized [ˈtronʲc]). Diphthongization compensates for the loss of the palatal stop (part of Catalan's segment loss compensation). There are other cases where diphthongization compensates for the loss of point of articulation features (property loss compensation) as in [ˈaɲ] ('year') vs [ˈajns] ('years').^[18] The dialectal distribution of this compensatory diphthongization is almost entirely dependent on the dorsal plosive (whether it is velar or palatal) and the extent of consonant assimilation (whether or not it is extended to palatals).^[19]

Portuguese[link]

The Portuguese diphthongs are formed by the labio-velar approximant [w] and palatal approximant [j] with a vowel,^[20] European Portuguese has 14 phonemic diphthongs (10 oral and 4 nasal),^[21] all of which are falling diphthongs formed by a vowel and a nonsyllabic high vowel. Brazilian Portuguese has roughly the same amount, although the European and non-European dialects have slightly different pronunciations ([ɐj] is a distinctive feature of Northern and Central Portuguese dialects). A [w] onglide after /k/ or /ɡ/ and before all vowels as in quando [ˈkwɐ̃du] ('when') or guarda [ˈɡwaɾdɐ ~ ˈɡwaʁdɐ] ('guard') may also form rising diphthongs and triphthongs. Additionally, in casual speech, adjacent heterosyllabic vowels may combine into diphthongs and triphthongs or even sequences of them.^[22]

In addition, phonetic diphthongs are formed in most Brazilian Portuguese dialects by the vocalization of /l/ in the syllable coda with words like sol [sɔw] ('sun') and sul [suw] ('south') as well as by yodization of vowels preceding /s/ or its syllable-final pre-consonantal allophone [ʃ] in terms like arroz [aˈʁojs ~ aˈʁojʃ] ('rice'),^[22] and /z/ (or its syllable-final pre-consonantal allophone [ʒ]) in terms such as paz mundial [ˈpajz mũdʒiˈaw ~ ˈpajʒ mũdʒiˈaw] ('world peace') and dez anos [ˌdɛjˈzɐnu(j)s ~ ˌdɛjˈzɐnu(j)ʃ] ('ten years').

Spanish[link]

Phonemically, Spanish has six falling diphthongs and eight rising diphthongs. In addition, during fast speech, sequences of vowels in hiatus become diphthongs wherein one becomes non-syllabic (unless they are the same vowel, in which case they fuse together) as in poeta [ˈpo̯eta] ('poet') and maestro [ˈmae̯stɾo] ('teacher'). The Spanish diphthongs are:^[23]

Italian[link]

The diphthongs of Italian are:^[24]

In general, unstressed /i e o u/ in hiatus can turn into glides in more rapid speech (e.g. biennale [bi̯enˈnaːle] 'biennial'; coalizione [ko̯alitˈtsi̯oːne] 'coalition') with the process occurring more readily in syllables further from stress.^[25]

Romanian[link]

Romanian has two diphthongs: /e̯a/ and /o̯a/. As a result of their origin (diphthongization of mid vowels under stress), they appear only in stressed syllables^[26] and make morphological alternations with the mid vowels /e/ and /o/. To native speakers, they sound very similar to /ja/ and /wa/ respectively.^[27] There are no perfect minimal pairs to contrast /o̯a/ and /wa/,^[3] and because /o̯a/ doesn't appear in the final syllable of a prosodic word, there are no monosyllabic words with /o̯a/; exceptions might include voal ('veil') and trotuar ('sidewalk'), though Ioana Chiţoran argues^[28] that these are best treated as containing glide-vowel sequences rather than diphthongs. In addition to these, the semivowels /j/ and /w/ can be combined (either before, after, or both) with most vowels, while this arguably^[29] forms additional diphthongs and triphthongs, only /e̯a/ and /o̯a/ can follow an obstruent-liquid cluster such as in broască ('frog') and dreagă ('to mend').^[30] implying that /j/ and /w/ are restricted to the syllable boundary and therefore, strictly speaking, do not form diphthongs.

Celtic languages[link]

Irish[link]

All Irish diphthongs are falling.

• [əi̯], spelled aigh, aidh, agh, adh, eagh, eadh, eigh, or eidh
• [əu̯], spelled abh, amh, eabh, or eamh
• [iə̯], spelled ia, iai
• [uə̯], spelled ua, uai

Scottish Gaelic[link]

There are 9 diphthongs in Scottish Gaelic. Group 1 occur anywhere (eu is usually [eː] before -m, e.g. Seumas). Group 2 are reflexes that occur before -ll, -m, -nn, -bh, -dh, -gh and -mh.

For more detailed explanations of Gaelic diphthongs see Scottish Gaelic orthography.

Cornish[link]

The following diphthongs are used in the Standard Written Form of Cornish. Each diphthong is given with its Revived Middle Cornish (RMC) and Revived Late Cornish (RLC) pronunciation.

Slavic languages[link]

Croatian[link]

• i(j)e, as in mlijeko^[31]

is conventionally considered a diphthong. However, it is actually [ie] in hiatus or separated by a semivowel, [ije].

Croatian dialects also have uo, as in kuonj, ruod, uon^[32] while, in Standard Croatian, these words are konj, rod, on.

Czech[link]

There are three diphthongs in Czech:

• /aʊ̯/ as in auto (almost exclusively in words of foreign origin)
• /eʊ̯/ as in euro (in words of foreign origin only)
• /oʊ̯/ as in koule

The vowel groups ia, ie, ii, io, and iu in foreign words are not regarded as diphthongs, they are pronounced with /j/ between the vowels [ɪja, ɪjɛ, ɪjɪ, ɪjo, ɪju].

Finno-Ugric languages[link]

Estonian[link]

All nine vowels can appear as the first component of an Estonian diphthong, but only [ɑ e i o u] occur as the second component.

There are additional diphthongs less commonly used, such as [eu] in Euroopa (Europe), [øɑ] in söandama (to dare), and [æu] in näuguma (to mew).

Finnish[link]

All Finnish diphthongs are falling. Notably, Finnish has true opening diphthongs (e.g. /uo/), which are not very common crosslinguistically compared to centering diphthongs (e.g. /uə/ in English). Vowel combinations across syllables may in practice be pronounced as diphthongs, when an intervening consonant has elided, e.g. in näön [næøn] instead of [næ.øn] < genitive of näkö ('sight').

closing

• [ɑi̯] as in laiva (ship)
• [ei̯] as in keinu (swing)
• [oi̯] as in poika (boy)
• [æi̯] as in äiti (mother)
• [øi̯] as in öisin (at nights)
• [ɑu̯] as in lauha (mild)
• [eu̯] as in leuto (mild)
• [ou̯] as in koulu (school)
• [ey̯] as in leyhyä (to waft)
• [æy̯] as in täysi (full)
• [øy̯] as in löytää (to find)

close

• [ui̯] as in uida (to swim)
• [yi̯] as in lyijy (lead)
• [iu̯] as in viulu (violin)
• [iy̯] as in siistiytyä (to smarten up)

opening

• [ie̯] as in kieli (tongue)
• [uo̯] as in suo (bog)
• [yø̯] as in yö (night)

Northern Sami[link]

The diphthong system in Northern Sami varies considerably from one dialect to another. The Western Finnmark dialects distinguish four different qualities of opening diphthongs:

• /eæ/ as in leat "to be"
• /ie/ as in giella "language"
• /oa/ as in boahtit "to come"
• /uo/ as in vuodjat "to swim"

In terms of quantity, Northern Sami shows a three-way contrast between long, short and finally stressed diphthongs. The last are distinguished from long and short diphthongs by a markedly long and stressed second component. Diphthong quantity is not indicated in spelling.

Semitic languages[link]

Maltese[link]

Maltese has seven falling diphthongs, though they may be considered VC sequences phonemically.^[33]

• [ɛɪ̯] ej or għi
• [ɐɪ̯] aj or għi
• [ɔɪ̯] oj
• [ɪʊ̯] iw
• [ɛʊ̯] ew
• [ɐʊ̯] aw or għu
• [ɔʊ̯] ow or għu

Sino-Tibetan languages[link]

Mandarin Chinese[link]

Rising sequences in Mandarin are usually regarded as a combination of a medial semivowel ([j], [w], or [ɥ]) plus a vowel, while falling sequences are regarded as one diphthong.

• ai: [aɪ̯], as in ài (愛, love)
• ei: [eɪ̯], as in lèi (累, tired)
• ao: [ɑʊ̯], as in dào (道, way)
• ou: [oʊ̯], as in dòu (豆, bean)

However, the four rising sequences below can be considered diphthongs as they are analogous to [ɨ], [i], [u] and [y] respectively and the bare vowel nucleus mostly only occurs along with the corresponding medial.

• e: [ɰʌ], as in hē (喝, to drink)
• ye/-ie: [jɛ], as in xié (斜, tilted)
• wo/-uo: [wɔ], as in wǒ (我, I)
• yue/-üe: [ɥœ], as in yuè (月, moon)

Tai–Kadai languages[link]

Thai[link]

In addition to vowel nuclei following or preceding /j/ and /w/, Thai has three diphthongs:^[34]

• [iɐ̯]
• [ɯɐ̯]
• [uɐ̯]

Mon-Khmer languages[link]

Vietnamese[link]

Vietnamese has a fairly large number of diphthongs:

• [iʊ̯] iu
• [iə̯] ia~iê
• [eʊ̯] êu
• [ɛʊ̯] eo
• [ɯɪ̯] ưi
• [ɯʊ̯] ưu
• [ɯə̯] ưa~ươ
• [ʌɪ̯] ây
• [ʌʊ̯] âu
• [ɤɪ̯] ơi
• [ɐɪ̯] ay
• [ɐʊ̯] au
• [aɪ̯] ai
• [aʊ̯] ao
• [uɪ̯] ui
• [uə̯] ua~uô
• [oɪ̯] ôi
• [ɔɪ̯] oi

Khmer[link]

Khmer language similarly has rich vocalics with an extra distinction of long and short register to the vowels and diphthongs.

• [iə̯]
• [ei̯]
• [ɐe̯]
• [ɨə̯]
• [əɨ̯]
• [ɐə̯]
• [ao̯]
• [uə̯]
• [ou̯]
• [ɔə̯]
• [eə̯̆]
• [uə̯̆]
• [oə̯̆]

Bantu languages[link]

Zulu[link]

Zulu has only monophthongs. Y and w are semi-vowels:

• [ja] as in [ŋijaɠuˈɓɛːɠa] ngiyakubeka (I am placing it)
• [wa] as in [ŋiːwa] ngiwa (I fall/I am falling)

See also[link]

• Hiatus
• Index of phonetics articles
• Table of vowels
• Monophthong
• Semivowel
• Triphthong
• Vowel
• Vowel cluster
• Vowel breaking
• Diaeresis

References[link]

Bibliography[link]

• Barbosa, Plínio A.; Albano, Eleonora C. (2004), "Brazilian Portuguese", Journal of the International Phonetic Association 34 (2): 227–232, DOI:10.1017/S0025100304001756 
• Bertinetto, Pier Marco; Loporcaro, Michele (2005), "The sound pattern of Standard Italian, as compared with the varieties spoken in Florence, Milan and Rome", Journal of the International Phonetic Association 35 (2): 131–151, DOI:10.1017/S0025100305002148 
• Borg, Albert J.; Azzopardi-Alexander, Marie (1997), Maltese, Routledge, ISBN 0-415-02243-6 
• Carbonell, Joan F.; Llisterri, Joaquim (1992), "Catalan", Journal of the International Phonetic Association 22 (1-2): 53–56, DOI:10.1017/S0025100300004618 
• Chițoran, Ioana (2001), The Phonology of Romanian: A Constraint-based Approach, Berlin & New York: Mouton de Gruyter, ISBN 3-11-016766-2 
• Chițoran, Ioana (2002a), "A perception-production study of Romanian diphthongs and glide-vowel sequences", Journal of the International Phonetic Association 32 (2): 203–222, DOI:10.1017/S0025100302001044 
• Chițoran, Ioana (2002b), "The phonology and morphology of Romanian diphthongization", Probus 14 (2): 205–246, DOI:10.1515/prbs.2002.009 
• Cruz-Ferreira, Madalena (1995), "European Portuguese", Journal of the International Phonetic Association 25 (2): 90–94, DOI:10.1017/S0025100300005223 
• Faria, Arlo (2003), Applied Phonetics: Portuguese Text-to-Speech, University of California, Berkeley, http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.134.8785&rep=rep1&type=pdf 
• Gussenhoven, Carlos (1992), "Dutch", Journal of the International Phonetic Association 22 (2): 45–47, DOI:10.1017/S002510030000459X 
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