[u]the high back vowel. The remarkbly brief nonsyllabic, however, is fast disappearing:
o lŭ > c lŭ ‘hole’
The diphthong [e] also has an appreciably limited occurrence.
orace ‘sky; heaven’
2.2.4.2.	Synaeresis or Cross boundary Diphthongization
Synaeresis is the process of unitization of cross boundary vowels. The diphthongized synergetic vowel is marked by a ^ under it and the diaretic or no diphthongized vowel by two dots under it
1. ta ‘went’ [synaeresis] go-past[=f] -sntmrkr ta- ‘is/was going’ [diaresis] go-tns [=f] -prg -sntmrkr [=f]   2. [losa mana-fi-e] ta- Los abel ate-VR-   sntmrkr go-imp ‘[Losa, it’s late] scram I’ [synaeresis] ni ta [diaresis] you-nom [=f] go-pst [=f] -Q ‘did you [sg.] go?’ 3 vu- ‘came’ [synaeresis] come-pst [=f] -sntmrkr vu- ‘is/was coming’ [diaresis] come-tns [=f] -prg 4 ct- ‘drank’ [synaeresis] drink-pst[=f]-sntmrkr c- ‘is/was drinking’ [diaresis] drink-tns [=f] -prg 5 šo- ‘drank’ [synaeresis] drink-pst [=f] - sntmrkr šo- ‘is/was drinking’ [diaresis]   drink-tns [=f] prg
2.2.4.3.	Phonemic Status of Diphthongs
Diphthjongs are single phonemes because their non-syllabics contrast with syllabic vowels as shown in 2.2.4.2 above. More minimal pairs are given below :
om ‘man; people’ omi ‘fire’ še ‘draw water from the well’ ši ‘knit’ imi ‘tail’ im ‘one; everyone; we [generic]’[as in ‘one should dress neatly’]
2.2.5	Vowel Clusters
Vowel clusters are sequences of two vowels. Unlike diphthongs, which are syllabic units, each of the vowels in vowel clusters constitutes a syllabic peak and carries a tone.
There are ten vowel clusters in Mao. They may be intramorphemic or intermorphemic.
io ōnķōzt ‘property’   crō, kąlió ‘eleven’   ōdzrķņ ‘elder brother’   crō pądió ‘fourteen’       it tō pfĭ ‘kind of snail’   ōcĭ ‘sister [speaker : male]’       to  crō kōsó ‘thirteen’   ōfōjąi ‘estate’   rbŏ ‘caraway plant’       eo khčŏ ‘curry’   ōnō  ‘property’   crō cącąņ ‘eighteen’   kąsņ ‘male friend’   khēnąŏ ‘bitter gourd’       oo ģvóŏ ‘dragonfly’   orō pōŊōō ‘fifteen’   prōcōŏ ‘fern’   orō cņrņó    ‘sixteen’