Modern kana usage

 is the present official "kanazukai" (system of spelling the Japanese syllabary). Also known as , it is derived from historical usage.
History.
As long ago as the Meiji Restoration, there had been dissatisfaction regarding the growing discrepancy between spelling and speech. On November 16, 1946, soon after World War II, the cabinet instituted the modern Japanese orthography as part of a general orthographic reform. The system was further amended in 1986.
General differences.
There were no small kana in the pre-reform system; thus, for example, would be ambiguous between "kiyo" and "kyo" while could be either "katsuta" or "katta".
The pronunciation of medial "h"-row kana as "w"-row kana in the pre-reform system does not extend to compound words; thus, was pronounced "nihon", not "nion" (via **"niwon"). There are a small number of counterexamples; e.g., "duck", pronounced "ahiru" rather than "airu", or , pronounced Fujiwara, despite being a compound of Fuji (wisteria) + hara (field). The h-row was historically pronounced as "fa, fi, fu, fe, fo" (and even further back, "pa, pi, pu, pe, po"). Japanese "f" () is close to a voiceless "w", and so was easily changed to "w" in the middle of a word; the "w" was then dropped except for "wa". This is also why "fu" is used to this day and has not become "hu".
The vowel + "(f)u" changes do not apply between elements of compound words, for example, the name was "Terauchi" not "Terōchi", as it is "Tera" (temple) + "uchi" (inside, home). The "-fu" of the modern "-u" series of verbs (that is, those verbs using the actual kana う, such as "kau" or "omou") was not affected by the sound changes on the surface; however, some reports of Edo era Japanese indicate that verbs like "tamau" and "harau" were pronounced as "tamō" and "harō" instead. In contrast, the -ō in "darō" and "ikō" is a product of the sound change from au to ō.
Furthermore, the topic particle "wa" , the direction particle "e" and the direct object particle "o" were exempted from spelling reform. In contemporary Japanese, the を-character is used only for the particle.
Examples.
Here, for example, ("a") includes "all" kana using the /a/ vowel, such as ("ka") or ("ta").
Regarding – these four morae are distinguished or merged to varying degrees in different Japanese dialects, with some dialects (Tōhoku and Okinawan, for example) merging all four into one, while other dialects (Tosa and Satsugū, for example) distinguish among the four. Standard spelling reflects the pronunciation of standard Japanese, which merges these into two sounds.