Editing Old Japanese (section)

===Vowels===
The Chinese characters chosen to write syllables with the Old Japanese vowel ''a'' suggest that it was an [[open vowel|open]] unrounded vowel {{IPA|/a/}}.{{sfn|Miyake|2003|pp=198–203}}
The vowel ''u'' was a [[close back rounded vowel]] {{IPA|/u/}}, unlike the unrounded {{IPA|/ɯ/}} of Modern Standard Japanese.{{sfn|Miyake|2003|pp=207–211}}

Several hypotheses have been advanced to explain the A/B distinctions made in {{tlit|ja|man'yōgana}}. The issue is hotly debated, and there is no consensus.{{sfn|Miyake|2003|p=62}} The traditional view, first advanced by [[Kyōsuke Kindaichi]] in 1938, is that there were eight pure vowels, with the type B vowels being more central than their type A counterparts.{{sfn|Miyake|2003|p=55}} Others, beginning in the 1930s but more commonly since the work of Roland Lange in 1968, have attributed the type A/B distinction to medial or final [[semivowel|glides]] {{IPA|/j/}} and {{IPA|/w/}}.{{sfn|Miyake|2003|pp=55–57}}{{sfn|Frellesvig|2010|p=32}} The [[diphthong]] proposals are often connected to hypotheses about pre-Old Japanese, but all exhibit an uneven distribution of glides.{{sfn|Frellesvig|2010|p=32}}

{| class="wikitable"
|+ Examples of reconstructions of type A/B distinctions{{sfn|Miyake|2003|p=62}}
|-
! ''i<sub>1</sub>'' !! ''i<sub>2</sub>''
! ''e<sub>1</sub>'' !! ''e<sub>2</sub>''
! ''o<sub>1</sub>'' !! ''o<sub>2</sub>''
! Author
|-
| {{IPA|i}} || {{IPA|wi}} || {{IPA|e}} || {{IPA|we}} || {{IPA|wo}} || {{IPA|o}} || Kikusawa (1935)
|-
| {{IPA|i}} || {{IPA|ï}} || {{IPA|e}} || {{IPA|ë}} || {{IPA|o}} || {{IPA|ö}} || Kindaichi (1938), Miller (1967)
|-
| {{IPA|i}} || {{IPA|ïj}} || {{IPA|e}} || {{IPA|əj}} || {{IPA|o}} || {{IPA|ə}} || Arisaka (1955)
|-
| {{IPA|ji}} || {{IPA|i}} || {{IPA|je}} || {{IPA|e}} || {{IPA|o}} || {{IPA|ɵ}} || Hattori (1958)
|-
| {{IPA|ji}} || {{IPA|i}} || {{IPA|je}} || {{IPA|e}} || {{IPA|wo}} || {{IPA|o}} || Lange (1968, 1973)
|-
| {{IPA|i}} || {{IPA|wi}} || {{IPA|je}} || {{IPA|e}} || {{IPA|wo}} || {{IPA|o}} || Unger (1977), Frellesvig and Whitman (2008)
|-
| {{IPA|i}} || {{IPA|ï}} || {{IPA|e}} || {{IPA|ɛ}} || {{IPA|o}} || {{IPA|ɵ}} || Ōno (1982)
|-
| {{IPA|i}} || {{IPA|ɨ}} || {{IPA|e}} || {{IPA|əj}} || {{IPA|o}} || {{IPA|ə}} || Miyake (2003)
|}

The distinction between ''mo<sub>1</sub>'' and ''mo<sub>2</sub>'' was seen only in ''Kojiki'' and vanished afterwards.
The distribution of syllables suggests that there may have once been *''po<sub>1</sub>'', *''po<sub>2</sub>'', *''bo<sub>1</sub>'' and *''bo<sub>2</sub>''.{{sfn|Frellesvig|2010|p=30}}
If that was true, a distinction was made between ''Co<sub>1</sub>'' and ''Co<sub>2</sub>'' for all consonants C except for ''w''. Some take that as evidence that ''Co<sub>1</sub>'' may have represented ''Cwo''.{{citation needed|date=September 2020}}