Why is katakana considered its own character set while the Latin capital letters aren't?


Everyone has agreed upon that Japanese has three sets of characters -
hiragana, katakana, and kanji.

Yet the Latin alphabet is considered to be one character set, even though the
capitals and lowercase letters differ just as much as the two kana.

Why is this the case?




**(1)** First of all, Japanese uses **5** separate scripts, not 3. They are:

>   * Hiragana
>   * Katakana
>   * Kanji
>   * Romaji
>   * Arabic Numerals
>

All of these scripts are used frequently in Japanese, so it is not correct to
say it only uses 3 scripts.

**(2)** Secondly, you ask why romaji are not considered to be two separate
scripts since they have upper case and lower case. You imply that
hiragana/katakana are analogous to upper case/lower case, but this is also
incorrect. The upper case and lower case variants of alphabet letters are
known as allographs [(see here for more
details)](https://en.wikipedia.org/wiki/Allography). This means that they are
simply variants of the same letter. In contrast, although hiragana and
katakana may represent the same phonemic sounds, they have distinctly
different characteristics. For example, Hiragana are used to represent verbal
inflections whereas Katakana do not. Katakana are used to represent loan words
in Japanese, whereas Hiragana are not. In short, there are many important
linguistic differences between the two scripts and since they have these
different functions, they are not considered to be just variants of the same
symbols (as is the case with upper case/lower case).




**(1)** First of all, Japanese uses **5** separate scripts, not 3. They are:

>   * Hiragana
>   * Katakana
>   * Kanji
>   * Romaji
>   * Arabic Numerals
>

All of these scripts are used frequently in Japanese, so it is not correct to
say it only uses 3 scripts.

**(2)** Secondly, you ask why romaji are not considered to be two separate
scripts since they have upper case and lower case. You imply that
hiragana/katakana are analogous to upper case/lower case, but this is also
incorrect. The upper case and lower case variants of alphabet letters are
known as allographs [(see here for more
details)](https://en.wikipedia.org/wiki/Allography). This means that they are
simply variants of the same letter. In contrast, although hiragana and
katakana may represent the same phonemic sounds, they have distinctly
different characteristics. For example, Hiragana are used to represent verbal
inflections whereas Katakana do not. Katakana are used to represent loan words
in Japanese, whereas Hiragana are not. In short, there are many important
linguistic differences between the two scripts and since they have these
different functions, they are not considered to be just variants of the same
symbols (as is the case with upper case/lower case).

