海

Sea, ocean; salt water. In early texts, it often functions as a conceptual boundary denoting the perimeter of the known world or the limits of civilization (e.g., "Four Seas" 四海). Metaphorically used to denote boundlessness, inexhaustibility, or vast capacity.

Used as a noun and as an attributive modifier meaning "maritime," "coastal," or indicating origin.

Distinguished from 江 (jiāng), which refers to fresh/fluvial water; a shift between these terms in a passage often indicates a movement from the interior to the coast. In later classical usage, 海 typically denotes coastal or near-shore waters, while 洋 (yáng) denotes the deep, open ocean.