当真 (dàng zhēn) has two uses: verb 'to take seriously/treat as true' (often negated: 别当真), and adverb 'really, truly' (more emphatic than 真). As a verb, it differs from the adjective 认真 (rèn zhēn 'serious, earnest'), which describes a person's attitude. As an adverb, it is similar to 着实 (zhuó shí), but 当真 focuses on literal truth while 着实 can intensify negative outcomes.