延长 (yáncháng) is a verb meaning 'to extend' or 'to prolong'—it refers to making something last longer in time or increasing its length in space. The character 延 (yán) means 'to stretch, to continue', often implying continuity or extension beyond an original limit; 长 (cháng) here means 'long' and contributes the sense of increased duration or physical length. Together, they form a compound that emphasizes deliberate, often beneficial, extension—such as extending a deadline, prolonging life expectancy, or lengthening a road.

This word is commonly used in formal, written, and professional contexts: government announcements, medical reports, project planning, and academic writing. It is neutral in register but rarely appears in casual speech (where people might say 拖一拖 or 多一点 instead). It can take direct objects (e.g., 延长假期) and often follows modal verbs like 可以, 应该, or 必须. It does not imply urgency or negativity by itself—unlike 拖延 (to delay/procrastinate), which carries a negative connotation.