遗留 (yíliú) is a verb meaning 'to remain as a legacy' or 'to be left over'—often referring to something unintentionally or unavoidably remaining after an event, process, or period of time. The first character 遗 (yí) means 'to lose', 'to abandon', or 'to leave behind', and often appears in contexts involving inheritance or remnants; the second character 留 (liú) means 'to stay' or 'to remain'. Together, they emphasize what persists despite change, removal, or conclusion—commonly used for physical traces, side effects, consequences, or historical imprints.

This word carries a neutral-to-slightly-negative connotation, especially when describing unwanted residues (e.g., medical complications, environmental contamination, or outdated policies). It’s frequently used in formal writing, news reports, scientific discourse, and official documents—not typically in casual speech. Unlike the more general 留下 (liúxià), 遗留 stresses involuntary, lingering presence, often implying difficulty in complete removal or resolution.