Why some particles such as "は", "を", and "へ" are spelled this way, not with "わ", "お", and "え"?
This is a very common question from those who are learning Japanese. And the fact is, the reason why we use these letters for these particles is not so well known even to Japanese people ourselves. (I myself was one of those who didn't really know why, so I did some research.)
Here is the answer:
(1) Such exceptions in modern Japanese usage are the legacy of the historical kana spelling systems.
For example, historically (until 1940s), words with "wa" sound (when "wa" sound is either at the end or in the middle of the word) used to be spelled with "は", instead of "わ".
(ex. かは（kawa; means river; spelled "かわ" in modern Japanese)
(2) The change in these historical kana writing systems took place as a result of one of many reforms carried out by the GHQ (General Headquaters) of the U.S. allied occupation in Japan, after the World War II, from 1945 to 1952.
(3) But when they conducted "Reforms of Japanese Language", they kept "は", "を", and "へ" as they are only for particle (=marker) uses.
If you are interested in this matter and wish to learn more, please read the article of "Hiragana" in Wikipedia, especially "spelling rules".
This is a very common question from those who are learning Japanese. And the fact is, the reason why we use these letters for these particles is not so well known even to Japanese people ourselves. (I myself was one of those who didn't really know why, so I did some research.)
Here is the answer:
(1) Such exceptions in modern Japanese usage are the legacy of the historical kana spelling systems.
For example, historically (until 1940s), words with "wa" sound (when "wa" sound is either at the end or in the middle of the word) used to be spelled with "は", instead of "わ".
(ex. かは（kawa; means river; spelled "かわ" in modern Japanese)
(2) The change in these historical kana writing systems took place as a result of one of many reforms carried out by the GHQ (General Headquaters) of the U.S. allied occupation in Japan, after the World War II, from 1945 to 1952.
(3) But when they conducted "Reforms of Japanese Language", they kept "は", "を", and "へ" as they are only for particle (=marker) uses.
If you are interested in this matter and wish to learn more, please read the article of "Hiragana" in Wikipedia, especially "spelling rules".