ひらがな or カタカナ when spelling out Onyomi readings?
I presume it doesn't really matter; however, I am curious what is generally considered correct. I have seen it done both ways.

For example.

日　＝　にち
Or
日　＝　ニチ

Which is preferred?

Question

ひらがな or カタカナ when spelling out Onyomi readings?
I presume it doesn't really matter; however, I am curious what is generally considered correct. I have seen it done both ways.

For example.

日　＝　にち
Or
日　＝　ニチ

Which is preferred?

Answer

Amateurs（common people） tend to use hiragana to just express sound. Hiragana is familiar than katakana. Professionals（teachers） tend to use katakana to express the sound comes from China. Kunyomi has meaning because it's original Japanese. Onyomi basically doesn't have meaning because it's imported sound. We use katakana to write loan words（imported sound）.

Answer

In dictionaries, I always see onyomi written in katakana, and kunyomi written in hiragana.