Why is 来る spelled with kanji and する is not?


来る and する are two irregular and most commonly used verbs. From my
observations, 来る is spelled with kanji. Even though there is a kanji version
of する 為る it is usually not used and I wonder why. Are there any cases where
the kanji version of する is used in modern Japanese?




The reading 為る【する】 is not a reading contained in the _jōyō kanji_ , which is
yet another reason it is not commonly used. (You don't learn about it in
school, you will have trouble publishing work with all instances of する
replaced by 為る, etc.)

The why has to be speculation, but to me it makes sense to drop the _kanji_
for the second-most used verb in the language; after いる, which derives from
居る, but is usually written in _kana_.

Of course, there is already the general convention to use only _kana_ for
subsidiary verbs, so that ～ている and also ～てくる will usually be written in
_kana_.

Something deserving a mention on the topic of する and _kanji_ is that there
exists an _ateji_ for the _renyōkei_ (し) of the verb する, namely 仕, which
appears in many common words such as

> 仕事、仕方、仕様、仕切る、仕業、仕入れ、仕上げ、仕送り、仕返し、…

In compounds, which are usually formed with the _renyōkei_ of a verb, the
_renyōkei_ of する is written in _kanji_. In that sense, one could say that する
does have a commonly associated _kanji_ , even if it is **not** used as
*`仕る【する】`.




The reading 為る【する】 is not a reading contained in the _jōyō kanji_ , which is
yet another reason it is not commonly used. (You don't learn about it in
school, you will have trouble publishing work with all instances of する
replaced by 為る, etc.)

The why has to be speculation, but to me it makes sense to drop the _kanji_
for the second-most used verb in the language; after いる, which derives from
居る, but is usually written in _kana_.

Of course, there is already the general convention to use only _kana_ for
subsidiary verbs, so that ～ている and also ～てくる will usually be written in
_kana_.

Something deserving a mention on the topic of する and _kanji_ is that there
exists an _ateji_ for the _renyōkei_ (し) of the verb する, namely 仕, which
appears in many common words such as

> 仕事、仕方、仕様、仕切る、仕業、仕入れ、仕上げ、仕送り、仕返し、…

In compounds, which are usually formed with the _renyōkei_ of a verb, the
_renyōkei_ of する is written in _kanji_. In that sense, one could say that する
does have a commonly associated _kanji_ , even if it is **not** used as
*`仕る【する】`.

