细心 (xì xīn) is an adjective meaning 'careful' or 'attentive', describing someone who pays close attention to details and avoids mistakes through thorough observation and thoughtfulness. The character 细 (xì) means 'fine', 'detailed', or 'minute', while 心 (xīn) means 'heart' or 'mind'. Together, they literally suggest 'a fine-tuned mind' — implying mental precision and conscientiousness rather than just physical caution.

This word is commonly used to praise people’s work habits, study methods, or daily behavior — for example, a student who double-checks homework, a nurse verifying medication dosages, or a chef adjusting seasoning with precision. It carries a positive, respectful connotation and often appears in feedback, recommendations, or character descriptions. Unlike the more neutral 小心 (xiǎo xīn, 'be careful'), 细心 emphasizes consistent, inherent attentiveness rather than momentary vigilance.