内心 + 的 + Noun
The noun 内心 (nèixīn) means "inner heart," "inner being," or "innermost feelings" and refers to a person's private thoughts and emotions. It is used to distinguish one's true feelings from outward appearances or expressions.
她表面上很平静,但内心其实非常紧张。
Tā biǎomiàn shàng hěn píngjìng, dàn nèixīn qíshí fēicháng jǐnzhāng.
She looks calm on the surface, but inside she's actually very nervous.
他的内心充满了对未来的期待。
Tā de nèixīn chōngmǎn le duì wèilái de qīdài.
His heart is full of anticipation for the future.
没人知道她内心真正的想法。
Méi rén zhīdào tā nèixīn zhēnzhèng de xiǎngfǎ.
No one knows what she truly thinks inside.