Lao is a little underdocumented compared to other languages, both in terms of actual linguistics and in terms of prescriptive norms.

There is a semivowel letter, ວ, which has a few roles:

  1. Consonant /v/ at beginning of syllable.
  2. Consonant /w/ at end of syllable.
  3. A long vowel diphthong at the syllable core: /u:ə/.
  4. Part of various vowels' orthographies which are spelled using a combination of two or more symbols: ◌ັວ /uə/, ◌ົວ /u:ə/, ◌ົວະ /uə/.
  5. A glide /w/ between a syllable-initial consonant and another syllable-core vowel.

I'm interested in the last role. I'm actually working on a Lao syllabifier / lexical analyser.

I'm sure I have read but cannot find the source that if a syllable has a tone mark it should be placed over the main initial consonant letter.

Normally there is only one such letter in the initial consonant, including a placeholder / glottal stop symbol for syllables which begin with a vowel.

But there are several digraphs which can commence a syllable: ຫງ, ຫຍ, ຫນ, ຫມ, ຫລ, and ຫວ. The diacritic in ຫຼ is a second Unicode character so it behaves like a digraph for my purposes too.

Then there are syllables of the form C + w + V where C is the initial consonant letter, w is the letter ວ, and V is a vowel. Since ວ is a semivowel it could be seen as part of a consonant cluster grouped with the preceding consonant or part of a diphthong grouped with the succeeding vowel.

In syllables without a tone mark the distinction is moot. But when there is a tone mark, does it belong over the C or over the ວ?

In some sources, such as my Lonely Planet Lao Phrasebook, words like ກ່ວາ (used for forming comparatives) have the tone mark over the consonant, before the ວ.

In other sources, such as SEAlang, the same word is only listed under ກວ່າ, with the tone mark over the ວ.

In Wiktionary there is automatic transliteration functionality for Lao which gives a correct transliteration only if the tone mark is over the C.

Spellings with the tone marks over the ວ always seem to have many more Google hits than the spellings with the tone marks over the C, but both always exist. However this could just illustrate that popular usage does not meet prescribed orthographic norms.

There is also much Lao text on the internet using old orthography so the moving tone mark could be a difference between old and new orthography.

I'm interested in finding the actual true current modern standard official orthographic rule covering this, if such a rule exists.

I'm also wondering whether there might be any ambiguous edge cases where two of the functions of ວ might run up against each other. Such as syllables beginning with /vw-/ or with /Cw-/ followed by any of the vowels spelled with a combination of symbols that include ວ.

  • Just a comment, whatever the rule is (I believe it's likewise Thai but have no proof), your code has to be tolerant to mistypes. Consider also sara-u plus a tone mark. Also, not every consonant can form clusters with w, there's only a limited set of those (in Thai). Aug 9, 2014 at 10:02
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    Remember that Lao underwent a fairly recent orthographic reform that Thai did not. There are quirkier things that happen in real text in the wild than just tone mark before top or bottom vowel as I'm finding out (-: I would appreciated a source identifying which consonant clusters are possible. Most are with k- and kh- but so far I've found a few others too. Aug 9, 2014 at 10:05

1 Answer 1


The spelling issues in this case are identical in Thai and Lao.

กว่า /kwaa/ (low tone) ‘more than’

กว้าง /kwaang/ (falling tone) ‘broad’

ด้วย /duay/ (falling tone) ‘also’

ด่วน /duan/ (low tone) ‘urgent’

Here are some examples from Thai. In the first two, the [w] letter is a glide, so the tone mark goes above or slightly after it. It is part of the onset consonant, not the rhyme. In the last two, the [w] letter is part of the rhyme, so the tone mark goes before it, over/after the consonant.

If you look at rhyming words, you could confirm this. For instance, /kwaa/ can rhyme with /khaa/, but /duan/ would not rhyme with words ending in –an, like /kan/ ‘with’. That’s because the [w] is part of the onset in the first case, part of the rhyme/coda in the second.

There are exact Lao equivalents for all the examples given, if you want to look them up. I recommend getting a good Lao dictionary if you want to learn about word shapes in the language.

  • In my experience so far there is no good current Lao dictionary. There best known or easiest to come by were in the old orthography. The one at the local foreign language bookshop uses an almost unreadable undersize typewriter Lao font. It seems that the one on SEAlang might be the best there is! Aug 6, 2014 at 0:41

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