Introduction
The word "diphthong" comes from the Greek and means "two voices" or "two
sounds." In phonetics, a diphthong is a vowel in which there is a noticeable sound
change within the same syllable. (A single or simple vowel is known as a
monophthong.) The process of moving from one vowel sound to another is called
gliding, which is why another name for a diphthong is a gliding vowel but they are
also known as compound vowels, complex vowels, or moving vowels. The sound
change that turns a single vowel into a diphthong is called diphthongization.
Diphthongs are sometimes referred to as "long vowels" but this is misleading.
While vowel sounds do change in a diphthong, they do not necessarily take more
time to say than a monophthong.
Diphthongs in American English
How many diphthongs are there in the English language? It depends on which
expert you ask. Some sources cite eight, others as many as 10. Even syllables
containing a single vowel can contain a diphthong. The rule of thumb is: If the
sound moves, it’s a diphthong; if it's static, it’s a monophthong. Each of the
following diphthongs is represented by its phonetic symbol.
/aɪ/ This diphthong creates sounds similar to "eye" and most often occurs with
letter combinations that include /i/, /igh/, and /y. Examples: crime, like, lime
/eɪ/ This diphthong creates sounds similar to “great” and is most often used with
letter combinations that include /ey/, /ay/, /ai/ and /a/. Examples: break, rain,
weight
/əʊ/ This diphthong creates sounds similar to “boat” and most often occurs with
letter combinations that include /ow/, /oa/ and /o/. Examples: slow, moan, though
/aʊ/ This diphthong creates sounds similar to “ow!” and most often occurs with
letter combinations that include /ou/ and /ow/. Examples: brown, hound, now
/eə/ This diphthong creates sounds similar to “air” and most often occurs with letter
combinations that include /ai/, /a/, and /ea/. Examples: lair, stair, bear
/ɪə/ This diphthong creates sounds similar to “ear” and most often occurs with letter
combinations that include /ee/, /ie/ and /ea/. Examples: beer, near, pier
/ɔɪ/ This creates sounds similar to “boy” and most often occurs with letter
combinations that include /oy/ and /oi/. Examples: oil, toy, coil
/ʊə/This diphthong creates sounds similar to “sure” and most occurs with letter
combinations that include /oo/, /ou/, /u/, and /ue/. Examples: lure, pure, fur
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Types of Diphthongs
Falling and rising
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; for that, 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 symbols (/aɪ̯ /, /ɪ̯ a/).
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 (see semivowel for examples).
Closing, opening, and centering
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]),[10] 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. These occurred
in Old English:
• beon [beo̯n] "be"
• ceald [kæɑ̯ld] "cold”
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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 [ʔau̯ɾ o] 'gold'
• ao [ao̯] 'a cloud’
Narrow and wide
Narrow diphthongs are the ones that end with a vowel which on a vowel chart is
quite close to the one that begins the diphthong, for example Northern Dutch [eɪ],
[øʏ] and [oʊ]. Wide diphthongs are the opposite - they require a greater tongue
movement, and their offsets are farther away from their starting points on the
vowel chart. Examples of wide diphthongs are RP/GA English [aɪ] and [aʊ].
Length
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. In languages with only
one phonemic length for pure vowels, however, diphthongs may 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. 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.
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Diphthongs in Dialects
One of the most interesting ways in which diphthongs relate to spoken language is
in how they’ve evolved into regional accents and dialects from their languages of
origin. In the borough Brooklyn, for example, when someone says, “Let the dog
out,” the word dog contains a distinctive “aw” sound so that “the dog” becomes a
“dawg.”
References
https://www.thoughtco.com/diphthong-phonetics-term-1690456
https://en.wikipedia.org/wiki/Diphthong#Types
