こんにちは！I am struggling to remember to use じつ or にち when it comes to the reading of things like “both days” (りょうじつ) or “which day” (なんにち). Does anyone have any tricks to remember when to use which on’yomi reading? I’m hoping there’s some sort of context that can help me differentiate.
A dictionary search tells me that にち is often at the beginning of a word. I guess one could argue 一日、毎日 and 何日 are a bit special?
For the other words I know like 平日 and 祝日, it’s じつ. It’s also something + ひ or び if the 日 is kind of slapped onto an existing compound.
If you know the answer is either にち or じつ then I suppose you can think that なん and にち both begin with the 'ん’ sound and it sounds better. Therefore, じつ must be the other one.
Even in the case of りょうじつ, you can say that both りょう and じつ end with the ‘う’ sound therefore they are matched together.
This is how I am thinking about it anyway, sorry if it isn’t useful!
Also - welcome to Wanikani! I am new myself.