长久 (cháng jiǔ) is an adjective meaning 'long-lasting' or 'enduring,' emphasizing duration over time—often with a positive, stable, or desirable connotation. The first character, 长 (cháng), means 'long' in terms of time or distance; the second, 久 (jiǔ), specifically means 'for a long time' or 'long-standing.' Together, they reinforce each other to express sustained existence, continuity, or persistence—not merely chronological length but also stability and resilience.

This word is commonly used to describe relationships (e.g., friendships, marriages), feelings (e.g., love, peace), commitments, or conditions that are meant to last. It often appears in formal or literary contexts, as well as in common expressions like 长久以来 (for a long time) and 愿你们幸福长久 (may your happiness last forever). Unlike more neutral terms like 长期 (chángqī), which refers to a defined extended period (e.g., long-term planning), 长久 carries emotional weight and implies desirability and continuity without end.