Khmer phonology

The phonological system described here is the inventory of sounds of the standard spoken language, represented using appropriate symbols from the International Phonetic Alphabet (IPA).

Consonants
The voiceless plosives may occur with or without aspiration (as  vs., etc.); this difference is contrastive before a vowel. However, the aspirated sounds in that position may be analyzed as sequences of two phonemes:. This analysis is supported by the fact that infixes can be inserted between the stop and the aspiration; for example ('big') becomes  ('size') with a nominalizing infix. When one of these plosives occurs initially before another consonant, aspiration is no longer contrastive and can be regarded as mere phonetic detail: slight aspiration is expected when the following consonant is not one of  (or /ŋ/ if the initial plosive is /k/).

The voiced plosives are pronounced as implosives by most speakers, but this feature is weak in educated speech, where they become.

In syllable-final position, and  approach  and  respectively. The stops are unaspirated and have no audible release when occurring as syllable finals.

In addition, the consonants, , and  occur occasionally in recent loan words in the speech of Cambodians familiar with French and other languages.

Vowels
Various authors have proposed slightly different analyses of the Khmer vowel system. This may be in part because of the wide degree of variation in pronunciation between individual speakers, even within a dialectal region. The description below follows Huffman (1970). The number of vowel nuclei and their values vary between dialects; differences exist even between the Standard Khmer system and that of the Battambang dialect on which the standard is based.

In addition, there are diphthongs and triphthongs which are analyzed as a vowel nucleus plus a semivowel (/j/ or /w/) coda because they can not be followed by a final consonant. These include: (with short monophthongs), , , , ; (with long monophthongs) , ; (with long diphthongs) , , , , and.

Syllable structure
A Khmer syllable begins with a single consonant, or else with a cluster of two, or rarely three, consonants. The only possible clusters of three consonants at the start of a syllable are, and (with aspirated consonants analyzed as two-consonant sequences). There are 85 possible two-consonant clusters (including [pʰ] etc. analyzed as /ph/ etc.). All the clusters are shown in the following table, phonetically, i.e. superscript ʰ can mark either contrastive or non-contrastive aspiration (see above).

Slight vowel epenthesis occurs in the clusters consisting of a plosive followed by /ʔ/, /b/, /d/, in those beginning /ʔ/, /m/, /l/, and in the cluster /kŋ-/.

After the initial consonant or consonant cluster comes the syllabic nucleus, which is one of the vowels listed above. This vowel may end the syllable or may be followed by a coda, which is a single consonant. If the syllable is stressed and the vowel is short, there must be a final consonant. All consonant sounds except and the aspirates can appear as the coda (although final /r/ is heard in some dialects, most notably in Northern Khmer).

A minor syllable (unstressed syllable preceding the main syllable of a word) has a structure of CV-, CrV-, CVN- or CrVN- (where C is a consonant, V a vowel, and N a nasal consonant). The vowels in such syllables are usually short; in conversation they may be reduced to, although in careful or formal speech, including on television and radio, they are clearly articulated. An example of such a word is មនុស្ស ('person'), pronounced, or more casually.

Stress
Stress in Khmer falls on the final syllable of a word. Because of this predictable pattern, stress is non-phonemic in Khmer (it does not distinguish different meanings).

Most Khmer words consist of either one or two syllables. In most native disyllabic words, the first syllable is a minor (fully unstressed) syllable. Such words have been described as sesquisyllabic (i.e. as having one-and-a-half syllables). There are also some disyllabic words in which the first syllable does not behave as a minor syllable, but takes secondary stress. Most such words are compounds, but some are single morphemes (generally loanwords). An example is ភាសា ('language'), pronounced.

Words with three or more syllables, if they are not compounds, are mostly loanwords, usually derived from Pali, Sanskrit, or more recently, French. They are nonetheless adapted to Khmer stress patterns. Primary stress falls on the final syllable, with secondary stress on every second syllable from the end. Thus in a three-syllable word, the first syllable has secondary stress; in a four-syllable word, the second syllable has secondary stress; in a five-syllable word, the first and third syllables have secondary stress, and so on. Long polysyllables are not often used in conversation.

Compounds, however, preserve the stress patterns of the constituent words. Thus សំបុកចាប, the name of a kind of cookie (literally 'bird's nest'), is pronounced, with secondary stress on the second rather than the first syllable, because it is composed of the words ('nest') and  ('bird').

Phonation and tone
Khmer once had a phonation distinction in its vowels, but this now survives only in the most archaic dialect (Western Khmer). The distinction arose historically when vowels after Old Khmer voiced consonants became breathy voiced and diphthongized; for example became. When consonant voicing was lost, the distinction was maintained by the vowel ; later the phonation disappeared as well. These processes explain the origin of what are now called a-series and o-series consonants in the Khmer script.

Although most Cambodian dialects are not tonal, colloquial Phnom Penh dialect has developed a tonal contrast (level versus peaking tone) to compensate for the elision of.

Intonation
Intonation often conveys semantic context in Khmer, as in distinguishing declarative statements, questions and exclamations. The available grammatical means of making such distinctions are not always used, or may be ambiguous; for example, the final interrogative particle ទេ can also serve as an emphasizing (or in some cases negating) particle.

The intonation pattern of a typical Khmer declarative phrase is a steady rise throughout followed by an abrupt drop on the last syllable.
 * ខ្ញុំមិនចង់បានទេ      ('I don't want it')

Other intonation contours signify a different type of phrase such as the "full doubt" interrogative, similar to yes-no questions in English. Full doubt interrogatives remain fairly even in tone throughout, but rise sharply towards the end.
 * អ្នកចង់ទៅលេងសៀមរាបទេ      ('do you want to go to Siem Reap?')

Exclamatory phrases follow the typical steadily rising pattern, but rise sharply on the last syllable instead of falling.
 * សៀវភៅនេះថ្លៃណាស់      ('this book is expensive!')