Editing Khmer language (section)

===Phonation and tone===
{{See also|Tonogenesis}}
Khmer once had a [[phonation]] distinction in its vowels, but this now survives only in the most archaic dialect ([[Western Khmer dialect|Western Khmer]]).<ref name=DiffZide /> The distinction arose historically when vowels after Old Khmer voiced consonants became [[breathy voice]]d and diphthongized; for example {{IPA|*kaa, *ɡaa}} became {{IPA|*kaa, *ɡe̤a}}. When consonant voicing was lost, the distinction was maintained by the vowel ({{IPA|*kaa, *ke̤a}}); later the phonation disappeared as well ({{IPA|[kaː], [kiə]}}).<ref name=ELL /> 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 language|tonal]], the colloquial Phnom Penh dialect has developed a tonal contrast (level versus peaking tone) as a by-product of the [[elision]] of {{IPA|/r/}}.<ref name=ELL />