延伸 (yánshēn) is a verb meaning 'to extend' or 'to stretch out'—either physically in space (e.g., a road stretching farther) or abstractly (e.g., an idea expanding into new areas). The character 延 means 'to delay' or 'to continue', carrying the sense of prolongation; 伸 means 'to stretch' or 'to extend', emphasizing physical or figurative reaching. Together, they form a compound that emphasizes continuous extension beyond an original boundary or limit.

This word is commonly used in formal and descriptive contexts—such as geography, urban planning, education, or logic—to describe how something spreads, develops, or propagates. It often appears with nouns like 道路 (road), 影响 (influence), 或 理论 (theory), and typically follows subjects performing the extending action. Unlike simple verbs like 伸 (shēn), 延伸 is more precise and less colloquial, rarely used in casual speech without a clear directional or developmental context.