Key takeaways
- Wikipedia counts 35 Khmer consonant letters, of which modern Khmer uses 33.
- Every consonant carries an inherent vowel, â or ô, which places it in the a-series or o-series.
- The series once marked voiceless and voiced consonants; Middle Khmer sound changes kept the vowel difference after voicing was lost.
- In a cluster, stops and fricatives outrank sonorants in deciding which series a following vowel takes.
- Two diacritics switch series: musĕkâtônd turns some o-series letters a-series, and treisăpt does the reverse.
Every Khmer consonant comes with a second piece of information attached: its series. Two letters can share the same consonant sound and still produce different vowels, because one belongs to the a-series and the other to the o-series. This article lists all 33 modern consonants by series, explains where the split came from, and covers the cluster and diacritic rules that decide the series when two letters meet. For how the whole syllable is assembled, start with the Khmer script explained. Romanised letter names below follow UNGEGN, as tabulated by Wikipedia.
Inherent â or ô: what puts a letter in a series
Wikipedia describes 35 Khmer consonant symbols, of which modern Khmer uses 33; two, ឝ and ឞ, are obsolete and kept for Pali and Sanskrit transliteration. Each consonant has an inherent vowel, either â [ɑː] or ô [ɔː], and that is the series: a-series letters carry â, o-series letters carry ô. A letter's spoken name is simply its sound plus its inherent vowel, so ក is called kâ and គ is called kô.
The series matters most when a dependent vowel is attached, because, as Wikipedia puts it, a consonant's series determines the pronunciation of the vowel symbols added to it. Khmer vowels explained gives both readings of every vowel sign.
Voiceless and voiced: why the split exists
The two series originally represented voiceless and voiced consonants, and Wikipedia notes they are still referred to that way in Khmer. During the Middle Khmer period, sound changes affected the vowels after voiceless consonants, and those vowel differences were preserved even after the voicing distinction itself was lost. The result is pairs such as ក and គ that are both pronounced [k] today but sit in different series.
Wiktionary gives a handy pair to remember the contrast. ក kâ, the first letter of the alphabet, is a-series and as a word means "neck". គ kô, the third letter, is o-series and as a word means "mute" or "deaf". Same consonant, different inherent vowel, different word.
All 33 consonants by series
| a-series (inherent â) | o-series (inherent ô) |
|---|---|
| ក kâ, ខ khâ | គ kô, ឃ khô, ង ngô |
| ច châ, ឆ chhâ | ជ chô, ឈ chhô, ញ nhô |
| ដ dâ, ឋ thâ, ណ nâ | ឌ dô, ឍ thô |
| ត tâ, ថ thâ | ទ tô, ធ thô, ន nô |
| ប bâ, ផ phâ | ព pô, ភ phô, ម mô |
| ស sâ, ហ hâ, ឡ lâ, អ 'â | យ yô, រ rô, ល lô, វ vô |
A worked example: counting the series
Count the table and the split is uneven: 15 a-series letters and 18 o-series letters, which adds up to the 33 Wikipedia gives for modern Khmer. Two patterns stand out.
- The nasals and most sonorants are o-series. ង, ញ, ន, ម, យ, រ, ល and វ are all o-series. Wikipedia explains that ណ nâ, originally an Indic retroflex letter, was adapted as an a-series counterpart of ន nô for convenience, and that all the other nasal consonants are o-series.
- The stops come in matched pairs. ក/គ, ខ/ឃ, ច/ជ, ឆ/ឈ, ត/ទ, ថ/ធ and ផ/ភ each pair an a-series letter with an o-series letter of the same sound in Wikipedia's table. ប and ព are not quite a pair: ប is [ɓ] before a vowel and [p] at the end of a syllable, while ព is [p].
Wikipedia also notes that ឋ, ឌ and ឍ are rare and occur only for etymological reasons in a few Pali and Sanskrit loanwords, so a beginner meets them far less than the rest.
When two consonants stack: the dominance rule
Khmer writes clusters by stacking the second consonant underneath the first in subscript form; every consonant except ឡ has one, and Wikipedia records the Khmer name cheung âksâr, "foot of a letter". When the two consonants come from different series, which one wins?
Wikipedia gives the rule: stops and fricatives are dominant over sonorants. The dominant consonant decides how a following vowel is read, regardless of its position in the cluster. When both members are dominant, the subscript consonant decides. In ត្រា tra [traː], for example, ត is a stop and a-series, រ is a sonorant, so the vowel ា takes its a-series value [aː]. Wikipedia adds that a dominant consonant can even change the inherent vowel of a later non-dominant consonant in the same word, though some longer words do not follow this.
Marks that move a letter to the other series
Because series is fixed to each letter, Khmer needs a way to write a sound with the "wrong" series. Wikipedia lists two diacritics for this:
- musĕkâtônd ៉, "mouse teeth", written above ង ញ ម យ រ វ to convert those o-series letters to a-series. On ប it instead turns the sound into p.
- treisăpt ៊, a wavy line written above ស ហ ប អ to convert those a-series letters to o-series.
When a vowel sign above the letter leaves no room, a vertical line under the consonant, kbiĕs kraôm, stands in for either mark. The same tools build the supplementary consonants for French and Thai loanwords, which Wikipedia describes as mostly digraphs made by stacking a subscript under ហ.
How consonants sound at the end of a syllable
Wikipedia sets out several final-position rules worth learning alongside the series:
- ដ and ឌ are pronounced [t] when final.
- ក and ខ become a glottal stop after certain vowels, including [aː] and [iə].
- រ is silent when final in most dialects.
- ស is pronounced [h] when final.
- A word cannot end in more than one consonant sound, so a subscript at the end of a word is not pronounced.
Learning the consonants in the app
Learn Cambodian, Speak Khmer begins with Khmer consonants, vowels and numbers, using pronunciation help, romanised spelling and tracing practice so the shapes become familiar. It is one of our language-learning apps. If you are coming from Thai, Khmer vs Thai script compares the two systems, and Lao tone rules shows a related idea, consonant classes, doing a different job.
Good to know
Frequently asked questions
How many consonants does the Khmer alphabet have?
What is the difference between the Khmer a-series and o-series?
Which consonant sets the series in a Khmer consonant cluster?
Why does Khmer have two letters for the same k sound?
Sources
- Khmer script (opens in a new tab)Wikipedia — accessed
- ក (opens in a new tab)Wiktionary — accessed
- គ (opens in a new tab)Wiktionary — accessed
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