保留 (bǎo liú) is a compound verb meaning 'to retain' or 'to preserve' — something kept intentionally rather than discarded, lost, or changed. The first character 保 (bǎo) means 'to protect' or 'to safeguard', and the second 留 (liú) means 'to leave behind' or 'to remain'. Together, they convey the idea of actively keeping something in its current state or location — whether it’s physical objects, rights, features, data, or even biological tissues. It’s commonly used in formal, administrative, medical, and technical contexts, but also appears in everyday speech when discussing choices like keeping an option open or maintaining a custom.

This verb is transitive and typically takes a direct object (e.g., 保留意见, 保留权利, 保留样本). It often implies intentionality and sometimes caution — for instance, doctors may recommend preserving tissue samples for future testing, or a company might retain customer data under privacy regulations. Unlike casual synonyms like 留下 (liú xià), 保留 carries a more deliberate, official, or long-term connotation.