noun
one's mind; inner feelings; the bottom of one's heart
Refers to one's true inner thoughts and feelings, often contrasted with outward expression. Used in formal or literary contexts.
彼の言葉からは、心裡に秘めた苦しみが感じられた。
From his words, I could sense the pain hidden deep in his heart.
心裡を打ち明けることは、容易ではない。
It is not easy to reveal one's innermost feelings.
Compound of 心 (heart, mind) and 裡/裏 (inside, back). The exact historical derivation is uncertain, but the combination naturally conveys the idea of the inner recesses of the mind.