Editing Vietnamese language (section)

===Vowels===
Vietnamese has a large number of [[vowel]]s. Below is a [[vowel diagram]] of Vietnamese from Hanoi (including [[centering diphthong]]s):

:{| class="wikitable" style="text-align: center;"
|-
! &nbsp;
! [[Front vowel|Front]]
! [[Central vowel|Central]]
! [[Back vowel|Back]]
|-
! [[Centering diphthong|Centering]]
| ia/iê {{IPA|[iə̯]}}
| ưa/ươ {{IPA|[ɨə̯]}}
| ua/uô {{IPA|[uə̯]}}
|-
! [[Close vowel|Close]]
| i/y {{IPA|[i]}}
| ư {{IPA|[ɨ]}}
| u {{IPA|[u]}}
|-
! [[Close-mid vowel|Close-mid]]/<br />[[Mid vowel|Mid]]
| ê {{IPA|[e]}}
| ơ {{IPA|[əː]}}<br />â {{IPA|[ə]}} 
| ô {{IPA|[o]}}
|-
! [[Open-mid vowel|Open-mid]]/<br />[[Open vowel|Open]]
|e {{IPA|[ɛ]}}
| a {{IPA|[aː]}}<br />ă {{IPA|[a]}}
| o {{IPA|[ɔ]}}
|}

Front and central vowels (i, ê, e, ư, â, ơ, ă, a) are [[Roundedness|unrounded]], whereas the back vowels (u, ô, o) are rounded. The vowels â {{IPA|[ə]}} and ă {{IPA|[a]}} are pronounced very short, much shorter than the other vowels. Thus, ơ and â are basically pronounced the same except that ơ {{IPA|[əː]}} is of normal length while â {{IPA|[ə]}} is short – the same applies to the vowels long a {{IPA|[aː]}} and short ă {{IPA|[a]}}.<ref group="lower-alpha">There are different descriptions of Hanoi vowels. Another common description is that of {{harv|Thompson|1991}}:

:{| class="wikitable" style="text-align: center;"
|-
! rowspan="2" |
! rowspan="2" | [[Front vowel|Front]]
! rowspan="2" | [[Central vowel|Central]]
! colspan="2" | [[Back vowel|Back]]
|-
! unrounded
! rounded
|-
! [[Centering diphthong|Centering]]
| ia~iê {{IPA|[iə̯]}}
|
| ưa~ươ {{IPA|[ɯə̯]}}
| ua~uô {{IPA|[uə̯]}}
|-
! [[Close vowel|Close]]
| i {{IPA|[i]}}
|
| ư {{IPA|[ɯ]}}
| u {{IPA|[u]}}
|-
! [[Close-mid vowel|Close-mid]]
| ê {{IPA|[e]}}
|
| ơ {{IPA|[ɤ]}}
| ô {{IPA|[o]}}
|-
! [[Open-mid vowel|Open-mid]]
| e {{IPA|[ɛ]}}
| ă {{IPA|[ɐ]}}
| â {{IPA|[ʌ]}}
| o {{IPA|[ɔ]}}
|-
! [[Open vowel|Open]]
|
| a {{IPA|[a]}}
| colspan="2" |
|}

This description distinguishes four degrees of vowel height and a rounding contrast (rounded vs. unrounded) between back vowels. The relative shortness of ''ă'' and ''â'' would then be a secondary feature. Thompson describes the vowel ''ă'' {{IPA|[ɐ]}} as being slightly higher ([[Near-open vowel|upper low]]) than ''a'' {{IPA|[a]}}.</ref>

The centering diphthongs are formed with only the three high vowels (i, ư, u). They are generally spelled as ia, ưa, ua when they end a word and are spelled iê, ươ, uô, respectively, when they are followed by a consonant.

In addition to single vowels (or [[monophthong]]s) and centering diphthongs, Vietnamese has closing [[diphthong]]s{{efn|In Vietnamese, diphthongs are ''âm đôi''.}} and [[triphthong]]s. The closing diphthongs and triphthongs consist of a main vowel component followed by a shorter semivowel [[offglide]] {{IPA|/j/}} or {{IPA|/w/}}.<ref group="lower-alpha">The closing diphthongs and triphthongs as described by Thompson can be compared with the description above:

:{| class="wikitable" style="text-align: center;"
|-
!&nbsp;
! colspan="2"| {{IPA|/w/}} offglide
! colspan="2"| {{IPA|/j/}} offglide
|-
! [[Centering diphthong|Centering]]
| iêu {{IPA|[iə̯w]}}
| ươu {{IPA|[ɯə̯w]}}
| ươi {{IPA|[ɯə̯j]}}
| uôi {{IPA|[uə̯j]}}
|-
! [[Close vowel|Close]]
| iu {{IPA|[iw]}}
| ưu {{IPA|[ɯw]}}
| ưi {{IPA|[ɯj]}}
| ui {{IPA|[uj]}}
|-
! [[Close-mid vowel|Close-mid]]
| êu {{IPA|[ew]}}
| rowspan="2"| –<br />âu {{IPA|[ʌw]}}
| rowspan="2"| ơi {{IPA|[ɤj]}}<br />ây {{IPA|[ʌj]}}
| ôi {{IPA|[oj]}}
|-
! [[Open-mid vowel|Open-mid]]
| eo {{IPA|[ɛw]}}
| oi {{IPA|[ɔj]}}
|-
! [[Open vowel|Open]]
| &nbsp;
| ao {{IPA|[aw]}}<br />au {{IPA|[ɐw]}}
| ai {{IPA|[aj]}}<br />ay {{IPA|[ɐj]}}
| &nbsp;
|}
</ref> There are restrictions on the high offglides: {{IPA|/j/}} cannot occur after a front vowel (i, ê, e) nucleus and {{IPA|/w/}} cannot occur after a back vowel (u, ô, o) nucleus.{{efn|The lack of diphthong consisting of a ''ơ'' + back offglide (i.e., {{IPA|[əːw]}}) is an apparent gap.}}

:{| class="wikitable" style="text-align: center;"
|-
! rowspan="2"|&nbsp;
! colspan="2"| {{IPA|/w/}} offglide
! colspan="2"| {{IPA|/j/}} offglide
|-
! [[Front vowel|Front]]
! colspan="2"| [[Central vowel|Central]]
! [[Back vowel|Back]]
|-
! [[Centering diphthong|Centering]]
| iêu {{IPA|[iə̯w]}}
| ươu {{IPA|[ɨə̯w]}}
| ươi {{IPA|[ɨə̯j]}}
| uôi {{IPA|[uə̯j]}}
|-
! [[Close vowel|Close]]
| iu {{IPA|[iw]}}
| ưu {{IPA|[ɨw]}}
| ưi {{IPA|[ɨj]}}
| ui {{IPA|[uj]}}
|-
! [[Close-mid vowel|Close-mid]]/<br />[[Mid vowel|Mid]]
| êu {{IPA|[ew]}}
| –<br />âu{{IPA|[əw]}}
| ơi {{IPA|[əːj]}}<br />ây {{IPA|[əj]}}
| ôi {{IPA|[oj]}}
|-
! [[Open-mid vowel|Open-mid]]/<br />[[Open vowel|Open]]
| eo {{IPA|[ɛw]}}
| ao {{IPA|[aːw]}}<br />au {{IPA|[aw]}}
| ai {{IPA|[aːj]}}<br />ay {{IPA|[aj]}}
| oi {{IPA|[ɔj]}}
|}

The correspondence between the orthography and pronunciation is complicated. For example, the offglide {{IPA|/j/}} is usually written as ''i''; however, it may also be represented with ''y''. In addition, in the diphthongs {{IPA|[āj]}} and {{IPA|[āːj]}} the letters ''y'' and ''i'' also indicate the pronunciation of the main vowel: ay = ă + {{IPA|/j/}}, ai = a + {{IPA|/j/}}. Thus, ''tay'' "hand" is {{IPA|[tāj]}} while ''tai'' "ear" is {{IPA|[tāːj]}}. Similarly, u and o indicate different pronunciations of the main vowel: au = ă + {{IPA|/w/}}, ao = a + {{IPA|/w/}}. Thus, ''<span lang="vi" dir="ltr">thau</span>'' "brass" is {{IPA|[tʰāw]}} while ''<span lang="vi" dir="ltr">thao</span>'' "raw silk" is {{IPA|[tʰāːw]}}.