Editing Japanese grammar (section)

====Historical sound change====
<div style="float:right; margin-left:2em;">
{| class="wikitable"
|+ Spelling changes
! Archaic !! Modern
|-
| {{nihongo||あ＋う|a + u}}{{pb}}{{nihongo||あ＋ふ|a + fu}} || {{nihongo||おう|ō}}
|-
| {{nihongo||い＋う|i + u}}{{pb}}{{nihongo||い＋ふ|i + fu}} || {{nihongo||ゆう|yū}}<sup>1</sup>
|-
| {{nihongo||う＋ふ|u + fu}} || {{nihongo||うう|ū}}
|-
| {{nihongo||え＋う|e + u}}{{pb}}{{nihongo||え＋ふ|e + fu}} || {{nihongo||よう|yō}}
|-
| {{nihongo||お＋ふ|o + fu}} || {{nihongo||おう|ō}}
|-
| {{nihongo||お＋ほ|o + ho}}{{pb}}{{nihongo||お＋を|o + wo}} || {{nihongo||おお|ō}}
|-
| auxiliary verb {{nihongo||む|mu}} || {{nihongo||ん|n}}
|-
| medial or final {{nihongo||は|ha}} || {{nihongo||わ|wa}}
|-
| medial or final {{nihongo||ひ|hi}}, {{nihongo||へ|he}}, {{nihongo||ほ|ho}} || {{nihongo||い|i}}, {{nihongo||え|e}}, {{nihongo||お|o}}{{pb}}(via {{transliteration|ja|wi}}, {{transliteration|ja|we}}, {{transliteration|ja|wo}}, see below)
|-
| any {{nihongo||ゐ|wi}}, {{nihongo||ゑ|we}}, {{nihongo||を|wo}} || {{nihongo||い|i}}, {{nihongo||え|e}}, {{nihongo||お|o}}<sup>1</sup>
|}

# Usually not reflected in spelling
</div>

Modern pronunciation is a result of a long history of phonemic drift that can be traced back to written records of the 13th century, and possibly earlier. However, it was only in 1946 that the Japanese ministry of education modified existing [[kana]] usage to conform to the {{nihongo|standard dialect|共通語|kyōtsūgo}}. All earlier texts used the archaic orthography, now referred to as [[historical kana usage]]. The adjoining table is a nearly exhaustive list of these spelling changes.

Note that the palatalized morae {{lang|ja|ゆ}} and {{lang|ja|よ}} ({{transliteration|ja|yu}} and {{transliteration|ja|yo}}) combine with the initial consonant (if present) yielding a palatalized syllable. The most basic example of this is modern {{Nihongo3|today|今日（きょう）|kyō}}, which historically developed as {{Nihongo3||けふ|kefu}} → {{Nihongo3||きょう|kyō}}, via the {{Nihongo3||えふ|efu}} → {{Nihongo3||よう|yō}} rule.

A few sound changes are not reflected in the spelling. Firstly, {{transliteration|ja|ou}} merged with {{transliteration|ja|oo}}, both being pronounced as a long {{transliteration|ja|ō}}. Secondly, the particles {{lang|ja|は}} and {{lang|ja|を}} are still written using historical kana usage, though these are pronounced as {{transliteration|ja|wa}} and {{transliteration|ja|o}} respectively, rather than {{transliteration|ja|ha}} and {{transliteration|ja|wo}}.

Among Japanese speakers, it is not generally understood that the historical kana spellings were, at one point, reflective of pronunciation.{{Citation needed|date=November 2022}} For example, the modern {{transliteration|ja|on'yomi}} reading {{Nihongo3||よう|yō}} (for {{Nihongo|leaf|葉|yō}}) arose from the historical {{Nihongo3||えふ|efu}}. The latter was pronounced something like {{IPA|[ʲepu]}} by the Japanese at the time it was borrowed (compare [[Middle Chinese]] {{IPA|[jiɛp̚]}}). However, a modern reader of a classical text would still read this as {{IPAc-ja|yō}}, the modern pronunciation.