I can say that after much research on this, I'm more thoroughly confused than before I started. I'm talking mostly about when they are used as suffixes, but the concept applies when they stand alone, or even start some words.
At first it seemed like
心 is used more to describe the core/root nature of something, and the other two are more for momentary/temporary states of mind. But I've found so many examples where the definitions appear to overlap that I'm just not sure any more. One dictionary definition I found comparing
念 indicates that
意 is a more temporary, outward appearance, while
念 is something deeper.
But again, there are many examples that I can find where I'm not sure of the nuances between them.
- 疑心・疑念・But no 疑意
- 信心・信念・But no 信意
- 念願・心願・But no 意願 → 念願 is like a "neutral" desire/wish, whereas 心願 conveys a religious desire/wish/prayer
- 専心・専念・専意 → All seem to mean the same
- 悪心（あくしん）・悪念・悪意 → First two similar (intent to do something bad), last is different (malice, ill will (toward someone))
- What are the nuances between these three?
- Are there any hard rules on when you can use them or not use them? (Like examples above - why isn't