‘详悉’ is a formal, literary verb meaning 'to thoroughly understand' or 'to have complete knowledge of' something — implying both depth and completeness of comprehension. The first character 详 (xiáng) means 'detailed' or 'elaborate', while the second 悉 (xī) means 'to know fully' or 'to be thoroughly acquainted with'. Together, they form a compound that emphasizes exhaustive, meticulous understanding — not just surface-level awareness but mastery through careful study or close observation.

This word appears most often in written Chinese: academic texts, official documents, medical reports, or formal speeches. It’s rarely used in casual conversation; native speakers typically choose simpler alternatives like ‘了解清楚’ or ‘完全明白’ in everyday speech. Because it carries a tone of seriousness and precision, 详悉 is especially common when describing expert knowledge — for instance, a doctor’s grasp of a patient’s condition or a researcher’s command of a technical subject.