expression, noun
inside one's heart; in one's mind
Refers to one's inner thoughts, feelings, or true intentions, often contrasted with outward expression.
心の中では、彼のことを尊敬している。
In my heart, I respect him.
彼女は心の中に深い悲しみを抱えていた。
She carried a deep sadness inside her heart.
内心 is more formal and often used in legal or psychological contexts, while 心の中 is a common, everyday expression for one's inner feelings.
本心 specifically means one's true feelings or real intention, whereas 心の中 is a broader term for the inner world of thoughts and emotions.
Compound of 心 (こころ, 'heart, mind') + の (possessive particle) + 中 (なか, 'inside'). A straightforward phrase meaning 'inside one's heart/mind'.