What's the difference between 鍵 and 鑰?


What is the difference between 鍵 and 鑰?

I was about to learn the kanji for 'key' and I came across this problem. When
I checked it in the dictionary it shows that both of them are read as kagi and
both mean key/lock. So I'm asking you for help.

[Please be understanding about my English 'cause it's not my native language.]




In short, the difference between 鍵 and 鑰 is that you can safely forget the
second one unless you prepare for the top level of kanji recognition test.

鍵 (on-reading: ケン) is the normal way to spell かぎ in kanji (and the only one to
spell ケン "key" in compounds, such as [鍵盤]{けんばん} "keyboard"). It is a part of
[Jōyō list](https://en.wikipedia.org/wiki/List_of_j%C5%8Dy%C5%8D_kanji), and
even the [guidelines for Japanese
newspapers](http://www.pressnet.or.jp/publication/book/pdf/shimbun_yogo.pdf)
explain that かぎ "key" is written with kanji 鍵. (Only do not confuse it with かぎ
"hook," which kanji is theoretically 鉤 but it is now spelt in kana anyways,
they even have the same pitch, [かぎ ]{HHL}.)

鑰 (on-reading: ヤク) is, unlike the one above, not a Jōyō kanji, or even a kanji
allowed in names. It definitely exists, and is a possible way to spell かぎ, but
no-one does that in modern texts, except maybe to show off. (I believe modern
Chinese uses 鑰 in its words for "key" as in implement for doors, while
reserving 鍵 for keys of piano.) There are some words that use 鑰 for its on-
reading, but they are extremely rare.

Hence, 鍵 is your friend. Write it, and do not worry about 鑰.

